Thoughts on making a waterproof (submersion proof) housing
2nd, Water and Wifi don''t mix so well. If the box is at water level your wifi is going to struggle quite a bit as the water will absorb a lot of the signal and you will run into what''s called the Fresnel Zone quite quickly as this is a function of how far above a given surface you are. The higher you can get the antenna above the water, the better.