Frequently Asked Questions

We have received many questions about the Odyssea and about wet submersibles in general. This document contains the questions, with answers, that were frequently discussed either by communications or at the DEMA shows. Questions are arranged by subject matter. Just click on the subject you would like to explore and you will be linked to that subject's section. If you have any other questions about either the Odyssea or about wet or dry subs, please contact us.



Batteries and Charging

Maintenance and Repair

Transport and Handling


Q. How safe is the Odyssea wet sub to operate?

A.Operating any underwater vehicle at an excessive ascent or descent rate can make it unsafe. Odyssea's design uses two methods to control the submersible's rate of ascent and descent. The first, and primary, method for controlling the subs depth is by a variable buoyancy system that operates similar to a diver's BC. Odyssea's variable buoyancy system makes up less than 5% of the total buoyancy on the sub. The other 95% of total buoyancy is fixed. The VB system was designed so that maximum ascent and descent rates are well within the recommended scuba rates of 60 feet per minute. Odyssea's maximum variable air buoyancy to mass ratio is 5%. A typical 185 pound diver using a BC has a buoyancy to mass ratio of 17%. Disregarding drag influences, acceleration (change in velocity or speed) is related to the mass and force on an object, therefore changes in the Odyssea's ascent or descent rates take place slowly. Maximum speed through the water is determined when an object's drag is equal to the applied force on it. The sub's drag in the vertical direction is higher than a diver's, so Odyssea will ascend at a slower rate. The second method for controlling depth is by adjustment of the thruster pitch angle during flight. This control function has designed in limitations to allow Odyssea to fly up or down only at small angles. Odyssea is much safer to use than any DPV since all DPVs can be pointed up and operated by inexperienced operators to ascend faster than the recommended maximum rates. Odyssea's occupants can also choose to exit the sub at any time during a dive should conditions become uncomfortable for them, making Odyssea much safer than any of the "air bubble" design underwater vehicles

Q.Why doesn't Odyssea use an air bubble for buoyancy and for its occupants as do flying bells or breathing observation bubble type personal submersibles?

A.Any ambient pressure underwater vehicle that uses an air bubble as the primary means of buoyancy can be not only difficult to operate but also potentially dangerous! There are two major operational weak points in the "air bubble" concept, potential for uncontrolled ascent or descent and unstable depth control. Any underwater vehicle that relies on nearly 100% of its buoyancy from air can experience air system failures which could either cause the sub to ascend or descend at high rates. Since divers using air bubble subs generally place their heads in the air bubble, they cannot readily exit the vehicle should one of these uncontrolled excursions take place. Many years of experience in the ocean environment with numerous underwater vehicles has shown us that the first reaction a person using an underwater vehicle has to anything "not normal" is to hold his or her breath. Uncontrolled ascents can therefore be extremely dangerous to the occupants of "air bubble" vehicles and has led to the notion that wet subs are generally unsafe. Stable depth control during flight is nearly impossible when operating "air bubble" vehicles due to the high volume of air used in the bubble. Small changes in pressure can greatly affect an "air bubble" vehicle's depth stability as the air bubble contracts or expands. Changes in depth can also occur as the occupants heads or shoulders are moved up in and out of the bubble. The only successful "air bubble" sub used today is the SportSub which has to use an electronic control system to regulate buoyancy.


Q. What are the advantages to operating the Odyssea wet sub?

A. The sub can carry equipment such as still cameras, video cameras, catch bags, lights, etc., leaving the diver unencumbered. Odyssea's variable buoyancy control system permits operators to retrieve and place items up to 30 pounds in water weight without having to transit back to the surface. Large battery capacity provides extended time underwater eliminating the need to frequently replace or recharge batteries. Divers using Odyssea to transit to various locations can greatly conserve air.

Q.Can divers using Odyssea get on or off at any time?

A.Yes, one advantage in flying on Odyssea is that divers use their own equipment. Consequently, they can get on or off at any time. The seat back tank recess helps to keep the divers on the sub and there are no restraints that prevent them from entering or exiting the sub. As long as the divers are neutrally buoyant, the sub will stay at the same depth when they get on or off.

Q.How stable and maneuverable is the wet sub?

A.Odyssea is very stable underwater and highly maneuverable. One or both of the divers can get off of the sub without effecting the sub's trim. The sub can also be operated with one or two divers. Changes in speed and ascent and descent take place slowly. Since the divers are not enclosed, the sensation of flight can still be felt. The sub can be kept on the bottom or at the surface when not in use.

Q.Can Odyssea be modified for specific operations or to carry additional equipment?

A.This wet sub can be easily modified to carry additional equipment or for specific projects due to its structural design and PVC fairing design. The aluminum structural frame permits drilling additional holes to install items and the front end design permits installation of cameras, lights, instruments and sonars. PVC fairings allow quick and inexpensive re-configuration of the sub's exterior when required. Electrical interfaces to the subs controls can be made through a blank plug installed on one of the battery pod hatches. Rebreathers can easily be adapted by changing the non structural seat back. Many other types of equipment can be installed for specific projects by the installation of modular, bolt on packages available from Odyssea Submarine. Packages consist of extra battery packs, extra air supplies for the occupants, camera support packages, extra thruster or custom packages as required by the user. These packages can be easily installed and interfaced to the sub for specific operations and removed when not required.

Q.Why doesn't Odyssea go faster than two knots?

A.A maximum speed of two knots, or about one meter per second, has been intentionally selected so that the sub safe and comfortable to operate with a high level of endurance. An open design for Odyssea was selected so there would be no restriction on visibility and allows the occupants to get on and off the sub at will. Increasing speed would make the diver feel more and more uncomfortable due to the effects that higher water velocity would have on his or her mask. Experience with DPV's has shown that speeds greater than two knots can depress the diver's regulator purge valve, causing the regulator to free flow. Odyssea can be made to go faster by the installation of a full front fairing, available from Odyssea Submarine, however this fairing will restrict access from the top of the sub.

Q.Doesn't a wet sub require an experienced pilot to operate it?

A.Odyssea's controls are so easy to operate that inexperienced persons can find that underwater flight can usually be made within 30 minutes after training. Two methods of control are supplied, depth and flight. The depth control uses a Buoyancy Control system that operates similar to a diver's BC. The flight control uses a single lever throttle that operates like a boat and a flight stick that is logically laid out and easy to comprehend.

Q.What documentation is supplied with the Odyssea?

A.A comprehensive manual is supplied with each Odyssea. This manual includes sections covering operations, deployment, maintenance, repair and troubleshooting. Assembly drawings and parts lists are supplied for all major assemblies. Odyssea's design was developed using AutoCAD and all systems are fully documented.

Batteries and Charging

Q.How long can Odyssea operate underwater before its batteries need to be recharged?

A.Odyssea has four batteries that have sufficient capacity to operate for at least three hours continuously at full throttle. Our tests have shown that the sub can complete five, one hour, average dives in a day before recharge is required.

Q.Can batteries be charged between dives?

A.Yes. The battery charger plugs into a connector at the top of the sub and the batteries and hatches stay in place during the charging process. This feature allows the batteries to be charged between dives to extend daily dive time. Charging may take place during transit to the dive site with the sub on the dive platform or deck of a boat or it can be charged at a dock.

Q. How long does it take to recharge the Odyssea's batteries?

A.Battery recharge time for a set of fully discharged batteries is within six hours. Charge time will be less according to the amount of battery usage during the prior dives. Battery capacity can be viewed on a gauge mounted on the sub's console.

Q.What is the useful life of Odyssea's batteries?

A.The AGM batteries used have a minimum cycle life of 600 discharges and recharges. Batteries can be purchased directly from the manufacturer for under $90 each. Gel type batteries can also be used but they experience approximately 250 cycles before they need to be replaced, have lower power density and are twice as expensive to replace.

Q.How are Odyssea's batteries charged?

A.Batteries are charged within the pod through a connector that plugs into the top of the sub. The charger is fully automatic and will monitor and automatically set the charge current as the batteries are charged. Once the batteries are fully charged, the charger switches to standby to prevent overcharging. The charger can be left on and connected to the batteries indefinitely without damaging the batteries. Charging Odyssea's batteries is a simple operation.

Q.Odyssea's batteries are installed in a one atmosphere pressure vessel. Battery charging takes place within the pod. How safe is this battery system?

A.Very safe and commercially proven. Storage batteries, including gel cells, can off-gas hydrogen and oxygen somewhat under some charging operations. An explosion will take place if these gasses are present in sufficient quantities and if there is an ignition source. Ignition sources can be caused by a battery short or spark within the power system. Most submersibles or Diver Propulsion Vehicles require that battery charging take place with the hatch cover off to reduce the potential for explosive gas build up. Odyssea has a single, double o-ring sealed, plug-in access cover for charging and uses three independent means to prevent dangerous battery gasses from building up during the charge cycle. Any of these means, by itself, would provide a safe system. The combination of the three assures battery safety above the level of any comparable commercial underwater vehicle. The first means for preventing battery gas accumulation AGM battery design that reduces the potential for off- gassing during charging. The batteries require no servicing or topping up with water. The second safety means is provided by installing Hydro Caps inside the battery pod. These devices convert any hydrogen and oxygen that could off-gas into water. The third means is provided by continually purging any battery gasses out of the pod during charging. As an added safety feature, Odyssea's power system is designed to reduce the potential for sparks and electrical shorts. The oil within the Thermoil batteries reduces the potential for battery shorts while sealed power components reduce potential for sparks.

Maintenance and Repair

Q.What type of maintenance is required for Odyssea?

A.Other than charging the batteries, refilling the scuba tanks and washing down the sub with fresh water after a dive, no routine maintenance is required. Depending on usage, the batteries will need to be inspected on either a six or 12 month interval.

Q.What is the operational life of the Odyssea's thruster motor?

A.Thruster motor brush life is 2000 hours equivalent to 400 days operating at 5 hours per day. Motors can be rewound at a local electric motor shop up to two times to provide 3000-4000 hours of additional operation before the motor needs to be replaced. Replacement motor cost is under $400.

Q.Underwater thrusters have been known to leak at the shaft seal area. What type of sealing arrangement does Odyssea's thruster use?

A.The thruster has two independent shaft seals for redundancy. The primary seal is a commercially proven submarine face seal. The back up seal is a lip type seal. Both seals are off the shelf and are rated for continual operations to 300 feet of seawater.

Q.How reliable is the thruster control system?

A.Very reliable and proven. Odyssea's electrical system uses an off the shelf sealed, solid state motor controller and switches that have proven for many years on golf carts. The controller and other electrical components are mounted on the inside of one of the battery pod cover plates.

Q.What components are likely to break during operations and how can they be repaired?

A.Components at the front of the sub will see the most abuse and wear during operations since that is where most of the diver's activity takes place. The fin rest at the front of the sub will likely be damaged first. Material for the fin rest is Lexan so it is highly impact resistant and only needs to be replaced should extensive damage occur. Normal cracks in the fin rest can be repaired by drilling a hole at the end of the crack to stop further crack propagation. Scratches on the fin rest during use can be extensive and unsightly on the surface but they will not be seen once the sub is underwater. Materials for a replacement fin rest can be purchased locally can be fabricated by cold bending to shape. The flight stick, throttle lever and VB lever are all mounted on bearings and could be damaged only by the application of excessive force. Since these control levers are aluminum they can be repaired by welding. The fairings are also subject to damage since they surround the structure but are non structural. Repair and replacement of fairings is covered in a following question. Odyssea's propeller could be damaged by foreign objects that enter the propeller. Since the maximum propeller speed is only 600 rpm, the likelihood for extensive damage is minimized. Propeller repairs can be made locally at a propeller shop since Odyssea's prop is fabricated from aluminum.

Q.How can Odyssea's systems be repaired should damage occur?

A.If experienced technicians are not available, the motor controls and thruster can be replaced independently in a modular fashion by unplugging the damaged component and plugging in a spare thruster or motor controller assembly end plate. Component replacement requires only a working knowledge of DC electrical power distribution and does not require a high level technician. Any automotive or marine electrician can diagnose Odyssea's electrical systems down to the component level with an inexpensive Volt/Ohm meter.

Q.. Are Odyssea's controls easy to maintain and what special tools are required for service?

A.All controls are mechanical for reliability and are easy to repair using common hand tools. Mechanical levers are used to control buoyancy, thruster pitch and steering making them easy and inexpensive to repair.

Q.What material are the fairings made from and how easy are they to repair, if damaged during operations?

A.. Fairings are non structural and are made from expanded PVC material that is resistant to ultra violet light. Damaged fairings can be field repaired by using a section of plastic or aluminum that can be used as a backing and pop riveted to the damaged area. The fairings can be easily repaired by removing the damaged fairing and locally fabricating a new one using the damaged fairing as a template. PVC fairings are easier, quicker and less costly to repair than fiberglass.

Transport Handling and Vessel Interface

Q.Doesn't Odyssea take up considerable room on the deck of a boat?

A.Odyssea's front fin rest folds up so deck space required is only 6 ft-8in long by 4 ft wide. The deck footprint is approximately the size of two lounge chairs. The sub can also be serviced and stored on the dive platform or on the deck of the boat.

Q.How do you launch, recover and transport the Odyssea?

A.The standard Odyssea weighs 770 pounds, requiring a lift or davit for deployment from a dive vessel. A single point lift pin located at the top of the sub is used to handle it in air. Hydraulic lifting platforms mounted to a boat's transom have been developed for jet skis and are ideal for deploying the Odyssea from a vessel that does not have a lift. Deployment from a dock at a resort can be made by using a lift or by trailer. The sub can be left on the dock or moved to another facility overnight for battery recharge and air resupply. Odyssea can be transported by trailer or in the bed of a pickup truck.

Links to other submersibles

Back to Odyssea's Home Page

©Copyright Odyssea Submarine, Inc., 1996-2005
All rights reserved.