Both the Centurions and Doc Terror utilize helicopters; however, these helicopters have only one rotor. A helicopter rotor generates great amounts of torque, and without either a second rotor or a tail rotor to counter the torque the helicopter would spin out of control.
When the Centurions are communicating using their wrist communicators, they are often shown on the receiving viewscreen at an angle that could not possibly be picked up by the wrist communicators, even showing their left arms which they wear their wrist communicators on.
The Centurions often go into space without wearing full body protection. Space has an average temperature of 2.7 Kelvin; it is far too cold for any exposure.
Mr. Ray's Depth Charger does not form a complete seal; without a complete seal, water would be able to get in around his arms.