Rowing tshirts have long been a source of hilarity, although more often than not the suggestions border on the unwearable and/or offensive, so much so they run the risk of arrest. But still... hilarious. One of my favourites in WA is from our friends at University boatclub, who wear tshirts saying "Frustrating umpires since 1897". Also accurate.
Anyway, here's a few we've either done, or thought of and discarded: