What Happened: From too many bangs against pilings, the screws, bolts, rivets, or adhesive that holds the rubrail in place has come loose. Plow into too many head seas or sit through a rainstorm and water will get below.
What You Should Have Done: At the end of each season, walk around the boat blasting the hull-to-deck joint with a hose. Have someone inside to watch for leaks.
27. Muffler Rot
What Happened: Water sat in a low point and rotted the muffler. Waves at the dock came in the transom exhaust ports and went directly into the boat.
What You Should Have Done: Feel under the mufflers or risers for moisture. They will ooze dampness months before giving way.
28. Frozen Muffler
What Happened: The drain plug on the bottom of the muffler or riser was removed but not replaced. Or you didn't drain them and the ice did its worst.
What You Should Have Done: Drain the water, but don't unscrew the plug and then go for drinks while it drains. You'll forget to put it back in.
29. Drain Plug
What Happened: You forgot to put in the transom drain plug when launching. Join the club. You're an idiot like the rest of us.
What You Should Have Done: Don't be an idiot-install a high-water alarm.
30. Hit By Another Boat
What Happened: The guy in the slip next to you hit your bow while tying to a dock. This forced the bolted-on swim platform on your boat to bang the bulkhead and loosen the bolts, which started to weep enough so that by the next morning all you saw was the VHF radio antenna.
What You Should Have Done: Do a Jackie Chan on the clown who smacked your boat. Then string him up by his nose hairs. There are some sinkings that just can't be prevented.