the battery be coated with a waterproof epoxy preventing water from contacting the terminals or bare wires and that all voids be filled with a non compressible liquid thus even though the interior of the central housing is open to the water the water will not contact the battery terminals within the central housing it is preferred that all housing voids containing moving parts be filled with a non conductive oil such as transformer oil or a silicon grease which is non compressible at operational depths this eliminates entrapped air which is compressible with the housing for the motor 22 for example filled with a non compressible non conductive liquid such as transmission fluid the seals between sections of the motor housing will have minimum strain placed upon them because the oil or fluid on the interior of the housing is non compressible and will act internally against the seals to prevent movement if air was entrapped within the housing this would be extremely compressible would not resist movement of the seals and thus would place an enormous strain upon the seals in order to keep the sea water out at operational depths it is also preferred that all voids even in the wires be filled with the non conductive non corrosive liquid to prevent the entry of sea water into those voids an example of this is shown in fig4 in which a typical joys tick switch 34 is illustrated the switch includes a switch assembly 54 having a pair of terminals 54 a and 54 b from which wires 56 a and 56 b extend the switch assembly has a threaded upper portion 57 at the top of which is a movable contact 58 a and a fixed.