the boat is open under the carpeted floor from the anchor hatch, to your aft cabin, which is under the driver seat.
so the water, from the rain, horn hole, windless, all drips down to the bilge pump as the boat goes fast in the water. That is what the forward bilge is for,
They split these two compartment from the engine room, because of the chance of carbon monoxide. So engine room has its own bilge and water will flow backwards under the fuel tanks to it.
Usually, the forward bilge is dead on an old boat, so i'd just check it.
Any drinking water line leaks will end up in your forward compartment , or leaking windows, leaking rub rail, or bow rail post leaking.
welcome to the wonder world of used boats....