88 Fourtrax 300 4×4 water/engine issues

I do a lot of river riding When I hit water too fast and it splashes up on the engine the engine wants to cut out and die. Any ideas on what is wrong and how to fix it. Doesn’t do it when I am crossing in deep water its more when I hit a shallow area fast and the water splashes up.

Also in air filter change should you coat the foam with oil?

Thanks