Mark Wahlberg Jumps into the New Year

Mark Wahlberg's swole body should be motivation to hit the gym -- at least until you quit your New Year's resolution in 3 weeks -- but his diving form might need some work.

Mark's been vacationing in Barbados with his wife and 4 kids and having a blast ... as you can see in these pics of the action star attempting a dive off a doc into the Caribbean.

Take off was strong, but midway Mark looks like he's heading for an awesomely painful belly flop.