How would i make all the players in my game a part of a collision group(besides the default one)?

In my place, the water i created is just a big brick(i wanted to reduce lag, so i didnt wanna do real water). And because the "water" is a big solid brick, that means my boats cant be boats, and instead are boat shaped cars with invisible wheels.

That all worked out.....but players and debris will now pile up on the water, which is not really a very realistic water effect... So i wanna make it so that my players and boats can go though the water, and only the boat wheels are the things that can sit on the water..