OK. You already have a wireless VP2. I saw no mention in your post of the Davis 6372 Wireless Temperature Station.
That has a cabled probe suitable for immersion in water (I run one in our spa, and one in our greenhouse).
It can be received and displayed on the VP2 console.
The Davis units are speced for ~1000 ft in open terrain. I have used them up to 1700' open, through trees and walls, and over 2000 feet LOS. Unless you have a mountain between the lake and the console, it should work. If it doesn't, Davis offers data repeaters, as well.