Vehicle Control drive motors/propellors positioning/thrusting motors - bilge pumps dive plane rudder elevator air valves - solenoid blood pressure armband air can bouyancy chamber weight in the bottom neutral bouyancy can be manipulated with thrusters.

Vehicle Sensors and Interaction actuator arm magnetic deployment device on arm release clamp on arm camera compass depth incline - accelerometer speed temp pressure internal water sensor DIY sonar array/mapping lasers for distance width mapping

Vehicle Manipulators actuator arm magnetic deployment device on arm 1 shot release clamp on arm camera speed DIY sonar array/mapping :D

lots of pictures and a discussion list

Waterproofing ideas: