Terry, I used cables that had sealed ends with o-ring seals. The connectors threaded together. The wires were encased in a sleeve that is molded to the connector. To pass the wire sleeve thru the bulkhead, or WTC deck, I used a cable seal. These have a pipe thread, or sealing nut and washer, and use a compression nut that seals against the wire sleeve.
A simpler alternative is to use single wires and compression fittings. Make sure that the wire ends are seals as the pressure can, and will , force H2O up the insulation of the wire and into the pressure hull.