Make sure your ship is fully stocked. You will use 40-60 Planks... 200+ cannonballs... maybe 40 bananas.
Atleast 1 person should board the skeleton ship. If the ship is close, make sure to bring a gunpowder keg to make the first holes. Make sure to prevent them from repairing and the sinking of the ship will go real fast!
Atleast 2 persons should stay aboard your ship to repair and hose. Especially the Dancing Demon and Foul Grog are rather hard, because the cursed cannonballs will spam and make you unable to repair and hose.
Position your ship
Stay with your alliance. make sure to raise all the sails and just turn your ship if necessary. The skeleton ships will only sail around your ship and it's easier to board them that way and just shoot and repair and not having to worry about sailing.
Communication is essential!
The person on the skeleton ship should inform the crew about the water level. Make sure to tell them to shoot lower or upper deck. The person on the skeleton ship should kill the minions which are repairing. Also you could assist your crew by taking out the cannon minions.
Sunk a ship?
Try to sail towards the sunken skeleton ship and as soon as the boat starts going UNDER water, start swiming towards it. You will see the boat disappear and see some possible loot. Take those.
Just before you have the loot back to your ship the new ship will spawn and it all starts over again. You have to kill 10 ships in about 6-8 waves or so. Sometimes there's 2 ships :-). You will hear the skull fort captain music at the last wave.
If MEG is also there.... You will use 40-60 more planks.... Make sure to destroy meg as soon as possible, or it will ruin your whole experience.