Did this just happen once? You might have backed off the throttle too fast and ingested water up the exhaust from backwash. Do you have flappers over the exhaust or baffles inside? You can suck water up the tailpipes if you back down too quickly.

I'd blow out the cylinders and fire it up and see if you are still getting water. Generally, you will only get water in one or two cylinders if there is a head gasket or manifold problem. The fact you have water in all cylinders tells me something else happened.

Don