When the weather turns warm, and even when it's still cold actually, the preppy douchebags start whipping out the boat shoes. In DC, one of my former places of residence, these ugly things are practically standard issue along with your brightly color Lacoste polo (with the collar popped), and your official douchebag-club membership card.
The rules of boat shoes are quite simple:
Unless you're within 30 feet of your own boat, you should never wear a boat shoe. Are we clear?
There are degrees to the offense
Just this morning, while walking back from getting a bagel, I saw a guy wearing boat shoes. His shorts and shirt were both decent. Were I on the pier in Cape Cod, I'd probably think nothing of it... but come on dude, you're walking down West Brodaway in Tribeca.
As a contrasting example, a few weeks ago we were dining at Otto (an upscale, trendy pizzeria in NYC) and there was a very high college douchebag quotient that night. Many of them were wearing boat shoes, with khakis, and blazers. As if these sad excuses for a shoe were somehow upscale, except for implying you might own a boat. I'm lucky I still had enough of an appetite to eat my dinner...
I suggest you pickup a much better summer shoe