how long have you had this boat ? you shoudl really be familiar with the basic plumbing esp. the location of all seacocks in case somethign happens.
if the head intake seacock is in the engine cpt, you shoudl be able to see it and check the hose for leaks. If it is under the cabin, chances are that's not the source of your problem as on gas boats engine and cabin bilges are usually isolated to prevent vapors or gas to get to the cabin.
basic water in the bilge troubleshooting :
do you find more water after using the boat ?
do you find more water after running the engine(s) but not driving the boat ?
do you find more water after it rains?
have you done any repairs or maintenance on the boat?
if you turn off the water pump for a while, does it help ?
if you're in salt water, is it fresh or sea water?
let us know...
in the meantime, take a good look around your engine compartment for signs of leaks. what kind of engines do you have ? leaky bellow on Mercs can results in water coming in and possible sinking.
dry the bilge as much as possible, with rags... and see if you can spot the water coming in... jsut a trickle of even drops ? years ago, i got water coming in the cabin bilge of my previous boat. i dried the areas i could reach and with a flash lights, i was a shinny line coming out of the hull itself. turned out water was coming in at the trasom from a issing transducer screw and wicking its way 15' forward !