Originally Posted by Steve - UK
What is "hydro locked" do you mean the engine seized? It would need a hell of a lot of water going in to do that, and with a filter on the end of the intake under the bonnet I cant imagine how it could happen - or have I miss understood?
Water is incompressible. It was a 2 litre engine, therefore only 0.5 litres to fill one of the cylinders. Add to that it will get heated so will expand therefore not requiring all 0.5 litres to fill one of the cylinders. The piston rises on the compression stroke and hydraulically lifts the cylinder head. When the piston is at the top of its stroke there's very little volume left in the combustion chamber so therefore you don't need the cylinder full of water to cause hydraulic lift. It wrote off the engine in the case of my mates.
Renault 19's were notorious for this as their air intake was low down and entering a deep puddle was enough for the engine to suck in the water.