Although they probably are not !.. But since I have never had experience with servos before, I better get the right answer from you guys…
I want to attach a propeller to the back of a toy-boat. The propeller would be running by a Hitec standard servo underwater… is that possible? 
(The microcontroller will be, however, above water-level)
If the answer is No, then are there any servos that can run underwater?
Thanks for the answers. 
can’t think of having ever seen any sealed servos. I think crust crawler used to have a simple thruster but now what they appear to have, while seemingly convenient, is like $1600USD a pop. 
hobby lobby sells a lot of boat oriented r/c gear among other things and what has caught my eye in the past is a “bow thruster” which really seems like it could be adapted for use as a propultion thruster, especially if you had two so a gyro could be used to keep a submersible tracking in a straight line. some boat drives have a gearbox attached to a DC motor and then they couple via u-joint to a long drive shaft, which has seals at the hull, and the prop on the outside end.
My Hitec 5980SG have got seals. But I don’t know if they are water proof.
I really dont think it would be wise to rund these servos under water.
Water will get in around the screws, output shaft, and servo wires. It will resist some moisture, but absolutely not submerged.
yah they are probably able to handle splash from rain or puddles better than normal hobby servos, but continuous immersion is another whole ballgame. a single o-ring or boot isn’t going to do the job for very long before water leaks in and messes with the electronics/motor.
A continuous rotation servo is about 60rpm, not going to move a lot of water with that. lol
Servos that are waterproof mean you can use them if it’s in a wet environment. Light drizzle or an occasional mud puddle encounter with an RC truck. I’m not aware of anything that is submersible.
Thanks EddieB and** Robot dude**,
I think I have an idea 
I’ll have the continuous rotation servo above water level, but, using gears, i’ll shift the propeller away from the Servo, i.e. downwards underwater !
And thanks to EddieB, good point, 60 rpm not gonna do much…!.. Hence, the gear-box that i’ll use will also double the speed of the propeller (120+ rpm something).
I guess, that will do the job !
Thanks for the answers everyone 
Guess I’d have to ask why use a servo at all to turn a prop? find a prop motor and prop for a model boat, and use it. It can be controlled fairly easily from your uP, if that’s part of the design.
Alan KM6VV
If the prop isn’t too large, an option might be to remove the gears on the top of the servo and drive the prop shaft directly off of the servo motor. Another idea might be to use a motor/prop setup like below and drive the motor using the control board inside the servo. Would be a way to have a bidirectional variable speed prop drive.
Why would you run a servo as a continuous motor? Like Jim said, the RPM on a continuous rotation servo isn’t very fast, you wouldn’t really get much with it.
If you’re trying to automate an RC boat, I would seriously just start with an RC boat as a platform. Then you can just mount a bot board 2 + a micro and control your servos/speed control with it…
servos and speed control both use PWMs as inputs…
Usually, the motor on RC boats are kept inside the body and it’s geared and shafted out to the propeller…
