"It is generally thought, for instance, that it was DevGru snipers who killed three Somali pirates standing next to a captive US merchant skipper in a small lifeboat last month. The frogman-commandos apparently hit all three men in the head with simultaneous single shots fired from the deck of a US destroyer nearby, having earlier arrived on the scene by parachuting into the sea."
News articles reported the lifeboat was pulled to within 40m of the ship. Whilst a rolling sea would add difficulty, I'd wager most run of the mill (so to speak) snipers would make the shot from 40m. If they're that elite at least quote something a touch more fitting that they've achieved. No Iranian hostage campaigns either.