I am almost done designing the mechanical systems of Nereid. I designed a trasmission mechanism, a joint for the fin and several other components to put the tail together and allow for interchangeble parts. I will wait for the first print of the robot to work on the fittings of several parts, since I can't ask a 3D printer to make precise clearances and interferences. 

Anyway what is left to do is choosing a servo motor, design the seals, design the dive planes and work on the electronics and buoyancy. 

Stay tuna!