From Business Insider –
Meet The "Seal Team 6", The Bad-Asses Who Killed Osama Bin Laden
The development of SEAL Team 6 was in direct response to the 1980 attempt to rescue the American hostages held in Iran.
The Team was labeled 6 at the time to confuse Soviet intelligence about the number of SEAL teams in operation at the time. There were only two others.
Team 6 poached the top operatives from other SEAL units and trained them even more intensely from there. Even among proven SEAL's the attrition rate for Team 6 is reported to be nearly half.
There are no names available for current Team 6 members, but the CIA does recruit heavily from their numbers for their Special Operations Group, so it makes sense that they were chosen to work with the CIA on this mission.