If You complete the indicated task You'll get the allotted gamerscore.
Big Booty (30) - Unlock all the secret ships.
Mine all mine! (30) - Collect over 5000 mines.
Master and Commander (20) - Win 15 gold stars in challenge mode.
Admiral (20) - Earn every type of medal.
Black Heart (20) - Win 50 Matches in total.
Death From Above (15) - Kill a non-airborne enemy while flying.
Ram ram ram the boats... (15) - Use the ram power up and kill two opponents in one go with it.
Sailing Pretty (10) - Win 7 stars in challenge mode.
Hoarder (10) - Win every championship.
Ka-boom! (10) - Sink two enemies with a TNT.
Cabin boy (5) - Complete the tutorial.