Check out this awesome Lego-powered submarine designed and built by the Brick Experiment Channel. This RC sub has magnetic couplings to transmit torque through the walls. No need to drill holes = no leaks.

Submarine specs:

– Displacement: 2.7 kg (6.0 lb)
– Test depth: 1.5 m (4.9 ft)
– Hull: glass food container (IKEA 365+ 1.8l), plastic lid
– Motors: 3x Lego XL-motor (8882-1)
– Magnetic couplings: K&J Magnetics R844-N52 neodymium magnet, TapeCase 423-5 UHMW Tape
– Propellers: Lego propeller blade (2952), Lego liftarms
– Radio control: 27 MHz controller dissembled from a toy submarine (Zantec Mini RC U Boot), L298 H-bridge to drive motors
– Power supply: 9V Lego battery box for the motors, 3.7V Li-Po for the RC
– Onboard camera: Faironly Firefly Q6
– Pressure sensor: Jolly Logic Altimeter One