Eric, there's always the great rc sub guy on youtube! I would touch base with him on his channel to inquire. He def knows his stuff.

https://www.youtube.com/@RCSubGuy

Thanks Chris, that’s helpful - I’d come to the same conclusion! Yes, it needs to be underwater (it’s for an RC shark I’m building) but I’m working on using a waterproof box instead for the servo, just in case the submerged time is longer than 30 mins.. do you know if these boxes are commercially available?

Hi Eric. I'd take statements on Ebay for cheap waterproof servos with a pinch of salt. Splashproof for vehicles maybe but that's about it.

Hitec make servos that are waterproof to the IP67 rating that means that they can be used underwater to a depth of 1 metre for up to 30 minutes. More expensive but if you want truly waterproof then this is the type of servo you need and from a trusted quality manufacturer like Hitec.

Are you looking to actually run the servo in the water or is this just in case of water ingress? Can you mount the servo in a box or housing as they do in submarines?

Thanks both for the reply – I checked on the listing for Traxxas servos and went into live chat – this was the response… unfortunately no good for a shark!

If they are advertized as waterproof then thay should be.
They must have been tested when they were desgined and made.

Eric! Traxxas makes decent waterproof servos. Here is their micro sub servo...

https://traxxas.com/2065a-waterproof-sub-micro-servo