The actor, who also appeared in The Fighter, was pulled from the water by a fire fighter and three teens after disappearing during a routine swim in the ocean.
The 54-year-old sparked concerns with local firefighters when they noticed how far out he was swimming.
Following a search of the water, an off-duty firefighter found him unconscious in the water, and performed CPR before Malone was transported to Boston Medical Centre.
Malone, who recently worked with John Travolta on the 2014 film The Forger, is now described as being in ‘critical condition’.
Speaking to the Globe, a spokesperson for the Boston FD, Steve MacDonald, said Malone's family is grateful for all those who helped the actor, adding:
'They're praying for the best.’
Our thoughts are with Sean Malone's family during this difficult time.