I have experienced my boat filling with water when some way offshore due to a veeeery small crack in the drivewell area.
Old salts do say that nothing shifts water faster than a frightened sailor with a bucket and I would be a bit dubiious about relying solely on a bilge pump as they do have a reputation for blocking up with bilge debris (in full sized boats).
I would also be a bit concerned if my only bilge pump solution involved operating with the hatch wide open because of the danger of swamping.
If you install a battery powered bilge pump then bear in mind that a) the pump will stop if the bilge water reaches the battery terminals and b) that when the battery runs flat the pumping will also stop
My solution is always to carry a carwash sized sponge in the centre hatch area (so I can reach it without getting my butt wet) and this proved sufficient to bale out the bilges at sea and allow me to get to shore safely for a complete bale-out and thence back to my start point. I was able to open and close the hatch between waves to sponge up water with the sponge - something I would have struggled to do with a "through-hatch" bilge pump.
FWIW the hull was probably about 1/3 full of water by the time I discovered the leak (this says something about the stability of the boat and the power of the mirage drive... or the dopey captain, though in his defence it just wasn't very apparent that there was a problem until the boat was that full!). I baled the hull out a bit before heading to shore, more to reduce my stress levels than to make the boat feel more seaworthy.
(P.S. Hobie very kindly replaced the hull under warranty without quibble).