I helped a friend do the same thing. Put a ball valve in the
sea water hose and connect it to a tee and connect the tee
to your water pump. The other opening in the tee gets another ball valve and
screw a garden hose adapter to it.
When you are using the garden hose you can open your
sea water valve so you don't over pressure your water pump. You will have
both valves close to each other and you can adjust your pressures
accordingly. You may also want to make a hard rubber garden type hose and
run it to your bilge. In an emergency you could use your engine water pump
to pump water out of your bilge. Put some kind of screen with a hose clamp
on the end of the hose.

Been there done that

Good luck
Charlie

PS Use good valves like Apollo, not the cheep imports.
Been there also