Trying to find serious water leak

After fishing for about 5 hours found a lot of water below deck in my 17 ft Searay, filled the back of boat with water. Checked for leaks on outside nothing, any ideas. Jus happened all of a sudden, last 2 times out. All areas for transducer, caulked. Live well was not in use. Help, I am baffled.

Found it leak was in the inlet for the live well, crack in fiberglass,let water in boat

It is an outboard

As crazy as it sounds check your drain plug.  I had a friend a few years ago who put his drain plug in the wrong hole and it stayed in there.  Boat filled up and after it drained we laughed a long time.  I still bust his chops on that one.  Other one to check if your boat is aluminum check under the "fins" my friend - same guy - had a screw from his bunk go through the fin and we took the boat out 2 times until we could find that leak.  Also check fitting on the livewell hose those can come loose.

Is this an I/O.  If it is it is most likely your driveshaft or shift bellows. 

inboard or outboard ?

Could be a fitting on the livewell hose or bilge. Next water visit plug the hose inlets below the waterline to see if the leak goes away.