Your Boat is Full of Holes
Not to be an alarmist, but your boat is likely already full of holes below the waterline. These can include holes for a drain plug, mounting bolts, transducers, sensors, through-hull valves and other items. In a perfect world, these — and any downstream hose clamps, fittings and strainers — would all be properly fastened, sealed and/or clamped to keep water out. And they likely were when the boat was brand-new. However, age, vibration (and pounding and slapping), thermal cycling, corrosion and other factors can work to loosen clamps and bolts and even cause structural cracks around fittings — all of which can result in leaks.