Underwater propeller

Hey guys,

I have a project where I need to find a propeller/impeller that would be able to move a person underwater but I'm finding it difficult to pick the right motor.

I'm looking for a motor that could propel a person for up to 5 km/h in either salt of freshwater.
I would prefer a brushless motor since I already have an Arduino based board with a 16A ESC installed (this one: https://hobbyking.com/en_us/dys-blheli-16a-mini-esc-with-soldering-pin-option-2-4s.html)

I'm also considering a dc continuous motor like this one http://www.ebay.com/itm/MABUCHI-MOTOR-RS-775WC-DC-6-18V-18000RPM-Drill-amp-Screwdriver-Garden-Tool-Toy-Motor-/142033945418

I recognize in that case I need either a low RPM motor or a gearbox that lowers the RPM to create torque.

I'm sorry if I might sound too vague and confusing but I've been searching the internet for a solution but can't find nothing relevant. The majority of posts talk about engines for karts but underwater it is a whole different thing with many variables to be taken into account.

Thank you

This is a microcontroller forum, you better ask in a diver/submarine forum about technical submarine questions.

I think you will be unpleasantly surprised by the amount of power needed to drag a body through the water at 5 KPH. The SeaDo Sea Scooter models use a 12V/8AH (96 Wh) battery. They run about 1 hour on a charge (cruising speed and 100 pound passenger) so that is close to 100 Watts. Max speed 3.2 KPH so let's say that cruising speed is 2.5 KPH. To double the speed to 5 KPH you will need four times the power: 400W. Of course a 400W motor is going to be bigger than a 100W motor so that will add drag. You will also need 400Wh of battery to keep going for an hour.

I like utopian ideas

However, you will have too many problems to solve.

Even if you got the right batteries and motor, you have to make sure everything is waterproof.
The motor and battery will create heat, so a plastic waterproof housing will not do the job. Even when emerged into water.

There are things, that you can hardly build yourself.

I think you will be unpleasantly surprised by the amount of power needed to drag a body through the water at 5 KPH

...particularly if that body is wearing scuba gear.

The lower price scooters are little more than pool toys.

Its a while since i sold my silent submersion, but i seem to recall its top speed was a lot less than 5kmh. High speed=uncomfortable and burns through battery faster.

The comment about plastic housings not being up to the job is just plain wrong, most scooter bodies are plastic (HDPE and the like).

if you want to do some googling "silent submersion" and "suex" are good starting points.

The tekna dpv's pop up on fleabay a fair bit, if you want something to tinker with.