1. Crab Pendants - Find and pick up four crab pendants.
You won't have to worry about finding these pendants on your own. I've described in the main part of the walkthrough where to find them.
2. Free the Captured Crew - Save nine crew members.
Once again, you won't have to worry about finding all nine cages. Their locations have been described in the main walkthrough section of the guide. You shouldn't have any major problems finding the cages, however you will have to leave one of the cages for later in order to deal with the rest of these objects. Otherwise you wouldn't be allowed to return to them.
3. Loot - Collect at least 1000 gold.
I'd strongly recommend that you read this description. The first mission was very simple when it came to having enough loot. Sadly, it's going to be more difficult this time. You will have to collect gold coins mostly from the bodies of fallen enemies. If you have some problems gathering enough money, try extending the final part of the mission. It's going to be very simple, because you would be attacked by endless groups of enemy thugs (if you chose not to perform certain activities).
4. Hit Combo - Perform a x15 hit-combo.
This is a very similar objective to the one from the first main mission of the game. As a result, it's going to be quite difficult to score such a combo. You could try and do it at the beginning of the mission, however it's going to be much easier to fulfill once you're on a raft (it's near the end of the mission). The choice is yours.