MegaCabMan said:when shrink wrapping connections I like to use a little black RTV on the wire then slide the shrink wrap over and heat it---seals up 100% water tight.
This is a great idea!
We have in the UK, shrink wrap, with some kind of resin type stuff already impregnated into the shrink wrap.
When you warm it all up, this stuff oozes out the ends and cools to a sealed, hardened finish.
You might be able to get this stuff in the US???
If not, try MegaCabMan's excellent idea.