On Wednesday, 1 May 2019 12:05:44 UTC+1, Tim Watts wrote:
Self amalgamating electrical tape. Dry everything, wrap several layers
*tightly* (this is key - the tape should stretch as you go - leave no
air gaps).

Self-amalgamating tape may be waterproof amalgamated to itself, but will it stick watertightly to PVC sheathing to prevent moisture creeping in?

I think some form of adhesive would be required for certainty

Owain