Captain Crawfish has a ship with the speed and cannons of a Phoenix Warbird. Attacking him with anything less has very, very little chance to succeed. His ship will repair itself as yours does (with the Shipwright).
When you have found and merged the 5 map pieces, and the new island Skullduggery appears, that is where Captain Crawfish is easily found. When you have a Phoenix Warbird, the Shipwright, and the Cannoneer, you are a match for him. He will not actually sink, but sail away when defeated.
(see related question)
*While it seems difficult at the start to imagine a million doubloons, each new, larger ship lets you earn more doubloons faster. Once you have 500,000, you can borrow another 500,000 from the bank and buy the Warbird. (You do not have to pay it back since you will already have the biggest ship.) The rest of the skilled crew are also easily affordable at this point, since the Phoenix Warbird generates a lot of doubloons with its massive cargo space.
Sail anywhere near the new island or the Pirate Outpost and he will eventually find you and attack.
First you get a bigger ship crew, then you go there kill captain crawfish
Captain Crawfish is defeated in battle on Skullduggery island, but appears again as a character on Super Villain Island (2012). He spends all but a tiny part of the island asleep.
Find the 5 pieces of the map and examine it and you'll see where skullduggery is. Dock there then get out of there and you'll find captain crawfish
There is nothing to be found on the hidden island (Skullduggery) until after you beat Captain Crawfish. After you defeat Captain Crawfish, the governor gives you a treasure location and a bone shovel. Sail to the hidden island. You will find the treasure under a mound, six paces right from the pirate flag.
Generally, sailing anywhere near the Pirate Outpost will bring him out. When you have all 5 map pieces and the new island appears, sail past that island and Captain Crawfish will soon attack. You will need the Phoenix Warbird, the Cannoneer and likely the Shipwright to best him in battle.
nothing. you will come here after you've beat Captain Crawfish and found the treasure map. (the treasure chest is on the island)
Once you have all 5 map pieces, one from each island, the small island appears near the Pirate Outpost. This is where Captain Crawfish generally appears even before the island becomes visible, but you can sneak in and dock rather easily. There is, however, nothing to do there until after you have beaten Captain Crawfish and gotten the treasure location from the Governor.
When you have all of the map pieces from the 5 trading islands, the 6th island (Skullduggery) appears near the Pirate Outpost. You cannot do anything there until you have beaten Captain Crawfish. This will require the largest ship, the Phoenix Warbird, as well as hiring the Shipwright and Cannoneer. Once you have beaten Captain Crawfish, go to see the governor and he will give you the directions to the buried treasure on the hidden island.
Once you defeat Captain Crawfish, and collect all five map pieces, you can go to the new island (Skullduggery) and dig up the buried treasure. Before you have done these two tasks, the island has no purpose. After Captain Crawfish has been chased away, the Governor will give you the treasure location and bone shovel. (In order to beat Captain Crawfish, you will need the strongest ship, the Phoenix Warbird.)
That is not the end of the quest. After Captain Crawfish runs away, sail to Fort Ridley and see the governor. He will give you a bone shovel and the location of the buried treasure. Sail to the hidden island (Skullduggery) and dig it up.
Once you defeat Captain Crawfish, and collect all five map pieces, you can go to the new island (Skullduggery) and dig up the buried treasure. Before you have done these two tasks, the island has no purpose. After Captain Crawfish has been chased away, the Governor will give you the treasure location and bone shovel. (In order to beat Captain Crawfish, you will need the strongest ship, the Phoenix Warbird.)