Justin Bieber posts nude picture of himself standing on the deck of a boat

Justin Bieber's fully naked ass hanging out on a boat deck ... or the gorgeous deep blue water of Bora Bora -- what are you really staring at in this pic?

It's okay. We'll give you a moment to think about your answer.

Justin just pulled his own version of "Break the Internet" ... with this nude pic of himself standing on the deck of a boat in the world famous lagoon.