Here's a good review of bilge pumps from a very informative site.

Yacht Survey

We currently have three electric pumps + two high water float switches (one midships and one aft) that are wired into the horn. We still mean to replace our rear pump with a larger one.

Two years ago we did install larger thru hull intakes/strainers that have built in diverter valves that could suck water from inside the hull if necessary.

Also 'Small boat safety at sea' looks like a good read.