I'd check all of your hoses first to make sure none are dry rotting or hard as a rock, if they are replace them they will fail. Also check all clamps, when possible double clamp ALL hoses in a boat, most builders do not, but should be doing so. You should check hoses atl;east once a season as a precaution anyways to stay safe.
If you have older plastic/nylon thru hulls, this would likely be the next likely cause, they crack from the sun and UV's and will allow water to seep in over time, this can be very very dangerous if you still have them. Best option is replace them with brass or chrome over brass, do not put in nylon again, they will again crack over time, do it once and be done for ever. You can coat the thru hulls with 3M 4200 as a quick fix, but this would be just to use the boat a few trips until work is done, not an actual fix.
If you use your wash down out on the water, it is possible your in deck acces hatches, the circular ones need new gaskets, they should be changed every 2 years at a min, and the ones you tend to open a lot more if your accessing something down there on a regular basis, might need to be replaced every year or sooner. The more they are opened, the more the gaskets wear and do not seal well, allowing water to get into the hull.
Other possibilities are that your getting spray over the bow and water is getting inthrough the anchor locker, this is a problem on some grady models more so then others and some water can accumulate this way. Also, it is possible the water was in the boat, but if you keep it on a trailer the boat is not level and does not drain fully when stored, and when on plane water moved aft in the boat, it could be standing water from rain etc that you only notice after running the boat and it moves and collects aft.
