Trial At Sea was the 27th produced episode and the 29th broadcast episode of the television series Joe 90.
Joe 90 races against time to prevent a new hoverliner being blown up by a bomb.
A warning that a bomb has been placed in the world's first Hoverliner is received by the company's chairman, Sir George Harris. The bomb is found, but then another telephone warning is received saying that the liner will be blown up on its maiden voyage. This time, however, the W.I.N. organisation has moved in, the telephone tapped and the mystery voice recorded. A search fails to reveal the existence of a bomb, but in the meanwhile Sam works on the voice pattern of the caller and discovers that it belongs to a man named Johnson Webb, who has a grudge against Sir George and his company. Sam visits him and secretly takes his brain patterns before handing him over to the police. The patterns are transferred to Joe, who is thus able to reveal that the bomb is, in fact, aboard the liner. It's of a deadly design, and Joe 90 is the only man who can handle it. There's a desperate race against time ahead of him to get to the liner and work on the intricate triple detonator mechanism which could set off the bomb and plunge the liner to its doom.
- The script gives Cope’s first name as Jack.
- Colonel White from Captain Scarlet and the Mysterons portrays Sir George Harris, while Doctor Fawn appears as a photographer at the dockyard.