All Aboard! Achievement
Board a ship without losing any crew members.
To unlock this achievement, you will need to cripple a ship and then approach it and initiate boarding action by holding . Once you do that, the entire time your crew are pulling your ship close and then actively boarding must be done without losing any of your crew. Since the enemy crew will be shooting muskets at you and your crew, this is partly luck. Set yourself up for success by upgrading your swivel guns and attacking a schooner since that only requires killing five enemy crew. If you see an explosive barrel on their deck, that can sometimes take out 2-3 crew with one shot. Speed is of the essence! If you run out of ammunition, or see your crew start to jump across, jump over as well and use smoke bombs to incapacitate everyone and finish your kills that way.
Note that if your crew jumps across, the swivel gun can kill them as well and that will obviously void the achievement as well.
*** Special Note *** Some people have reported that this would not unlock for them when attacking schooners. If that happens for you, try a brig instead as the next smallest ship.