You'd use some standard tether cable, Blue Robotics sell good stuff for that.

https://bluerobotics.com/store/cables-connectors/cables/fath...

Then just straight onto the screw terminals.

I need it to be on the bottom if the lake. Trying to keep fisherman from snagging it too

You might be better off with directional wifi antennas if appropriate for your application.

House in the way. Although I could blast high power through my neighbor’s bedroom, it feels rude.

Fiber I recon.