Also, engine
and batteries in water tight compartments vented to the
deck (always - rising water kills the engine and or
electric pumps/radio).

Batteries should ideally be in watertight boxes but should also drain
(in case of charging gas escaping) to prevent danger of explosion. So
this is paradoxical to start with. And second, if the engine is not
sealed off, you can divert the raw water intake to pump out incoming
water in the engine compartment. This can off course also be done with
other means but an engine sure is a powerful and reliable pump!
As long as you make sure electrical boards are higher than the engine's
air intake, both will continue working untill it's really too late. But
by that time buoancy will be so diminished, you won't be using power or
engine anymore.

And always remember: the best means of getting water out is a scared
person with a bucket :-)

Victor (currently installing the 4th pump in the bilge - 1 engine, 2
electrical, 1 manual)