Explanation for stupid folks like me? What is that?

Answer from comment chain: drain plug from a boat. Without it boat floods, used to drain boats before towing

Story time!

Drunk dad takes me and my Boxer pup on the lake in our crappy little boat. Great times! Until we stopped for a minute to rescue dog overboard. Then we start sinking, plug's laying on the deck, and the motor won't start. Then dad falls out trying to get the dog. At this point we're up to the fucking gunwales with water. Never saw dad panic before or since, guess he couldn't swim, but he was flooding the boat trying to scramble back in.

Forgot how I managed, but got it beached on the closest shore. Dad bails of the boat with his cookie tin full of pot, terrified it got wet. It wasn't, so he rolled a joint.

Boat won't start because the battery was underwater too long, dead as a sack of hammers. I take his keys and start on the 12-mile walk back to the car. 10-miles of dragging that fucking dog down that country road. Why dragging? Because it got dark and I had trained her to not move when she saw headlights coming. Fuck me. Why 2-miles short? Because dad came driving up!

So many lessons learned that day. #1 was probably: Just walk to the nearest house and ask for help. Fuck me.

(This was in the early 90s, no cell. Dad actually had a car phone, for all the good it did.)

Next time I'll tell y'all about me and the boys sinking my canoe. That was a great camping trip.

This happened twice to me and my Dad. The last thing we usually do when talking the boat out of the water is remove the drain plug. It is kept in the boat’s glove compartment, when not in the water. Both times we noticed pretty quickly and were able to get it back on the trailer and pull it up to drain.

I don't even know what I am looking at here.

Pull it like a grenade pin and throw it as far away from the boat as possible (into the water)

Is that some kind of oil plug for a car?