To jokeboat is to add superfluous and obvious information to a joke (especially someone else's), usually in a misguided attempt to explain the joke (often because the jokeboater didn't get it initially (<i>i.e.</i> "Missed the Boat on the Joke)).
"Those bees are evil- you'll never find a more wretched hive of scum and villany".
"Oh, dude, that's funny, since bees LIVE IN A HIVE!!!"
"Right; that was the point. Quit jokeboating".