The manipulator for my Seafox was hacked from a Radio Shack Armatron toy. It's just a basic claw with open and close function, which is accomplished buy means of a motorized planetary gearbox. The gear box is sealed in the same type of housing I designed for my Stinger Thrusters but this one has an actual seal on the shaft.
Unfortunately the first time I took the rov out with the manipulator it turned out I forgot to put Teflon tape on the treads of the plug to the housing and it filled with water and which caused me all kinds of buoyancy problems. I forget to dry the motor out and unlike the small radio shack motors I use in my camera mount this one rusted up solid and has to be replaced. Live and learn I guess.