The two critical things are keeping the electrics and the engine air filter inlet orifice free of water, (not the inlet manifold, which is part of the engine). To be sure, this means driving through anything over a couple of inches of water depth at about 2mph. Plus, as mentioned, keep your revs up.
. (The Renault Espace air inlet was originally placed very low down by the front axle, and caused owners all sorts of problems in floods. Similarly, the Austin Mini distributor was placed low down and faced the left front wheel, making it very susceptible to getting wet).
I despair at news reports on TV where drivers zoom through foot-deep water without a care in the world. It's utterly crazy, and asking for trouble.