Yes, but it is easier than it sounds.
Yes. Until you defeat the Captain, the governor will not give you the directions to the treasure buried on Skullduggery.
you get a ship defeat the evil capt. crawfish then you win
the mayor guy gives it to you at the mansion once you defeat captain crawfish.
well after you defeat Captain crawfish you enter skullduggery island. after finding nothing you head back to the main island and talk to the guy in the governor's house, he will give you a treasure map and shovel from there you go bak to skulduggery and meet captain crawfish to whom you defeat.
You will need to amass your doubloons to buy larger ships, because only the largest, the Phoenix Warbird, stands a chance against Captain Crawfish. (see related question)
Nothing. Captain Crawfish was there. But you don't exactly do anything on Skullduggery island. You defeat Crawfih on sea.
first you get money and upgrade your ship for 1000000 to the warship then you go and find the map after that you go and defeat captain crawfish
Once you have the Phoenix Warbird, with the Shipwright and Cannoneer aboard, you can battle Captain Crawfish. Once you defeat him, you get the location of the treasure on the new small island. Go there to dig it up. You will not see Captain Crawfish's ship once you get the treasure location and the shovel from the governor. He will show up when you are digging.
After you defeat Captain Crawfish. Assemble the map from the five pieces to reveal the hidden island (Skullduggery). Then continue trading until you have the largest ship, the Shipwright, and the Cannoneer. That will let you defeat Captain Crawfish. Once you have beaten him, go back to see the governor at Fort Ridley to get the directions to the buried treasure.
All of the ships larger than the raft have cannons, but you need the biggest ship, the Phoenix Warbird, to beat Captain Crawfish. As you can afford each larger ship, trade up to get cargo and doubloons faster.
use your fully upgraded grapple grounder
Yes. If you try with smaller ships, he invariably slips away to repair his ship. (see related question)