The uniform Don Knotts is wearing during the "Super Doodle Dandy" scene is a Commodore Royal Naval Maritime Uniform.
A limpet is a type of sea snail. A Limpet Mine is an explosive with a magnet so it can be attached to a metal ship. Since the mine sticks to the boat like a snail would, they are called limpet mines and usually attached by undersea divers or commandos .
This was the final animated film work released by Warner Brothers before the animation studio was shut down. Warners would continue to release theatrical shorts produced by Depatie-Freleng Enterprises until 1969.
The premiere was shown in a huge underwater theater at Weeki Wachee Springs, Florida.