The Haven Island Add-on for HITMAN 2 has 7 achievements worth 150 gamerscore.
Complete The Last Resort.
Make like the famous Aussie and leave.
Shoot for gold and look to the sea.
Complete all Mission Stories for The Last Resort.
Complete The Last Resort on Master Difficulty.
Select a Starting Location and use an Informant to smuggle an item onto Haven Island.
Reach Haven Island Mastery Level 20.