This guide is suitable for current RuneScape and Old School.
Talk to Bill Teach who can be found in the pub in Port Phasmatys, east of Canifis.
Bill will inform you that he is in need of a pirate to sail with, and will ask if you would like to join him. Tell him you are and he will ask you to board his boat, The Adventurous, when you ready. Head down to the docks and climb aboard the most eastern boat and speak to Bill to set sail. Shortly following your departure a cutscene will appear in which you are attacked by an enemy boat. Bill will ask you to swing across to that boat and destroy their cannon.
Defending from the boat
Climb below deck and search the gun locker to get a fuse, and then search the repair locker and collect four ropes. Collect the tinderbox lying on the floor, and then go back up to deck. Find the climbing net to the south and climb up it, and then use a rope with the hoisted sail directly above you. You'll swing across to the other boat, losing your rope in the process. Now use the fuse with the barrel next to the cannon, and then light the fuse with the tinderbox. The barrel will explode, destroying the cannon in the process. Climb up the climbing net and use your second rope with the hoisted sail to return back to The Adventurous.
Repairing the ship
Report back to Bill and he will now ask you to repair the holes below deck. Climb down and search the repair locker, selecting 6 repair planks, 3 swamp paste, 30 tacks and hammer. Use the repair plank with the hole, and then waterproof it with the swamp paste. Repeat this for the other two holes.
Climb back up deck and inform Bill you have repaired the holes. Bill will now ask you to plunder the enemy ship, and will ask for you to get 10 plunders. Climb up the southern climbing net and use another rope with the hoisted sail to swing across. Climb below deck and plunder the storage chest, barrel and crate until you receive 10 plunders. If you don't get 10 plunders at first, wait for the plunders to respawn or log out to quickly reset the items. Return back to The Adventurous and climb below deck and use the plunder with the storage chest. Speak to Bill and he will ask you to repair the ships cannon.
Shooting the pirates
Get a cannon barrel from the gun locker below deck and then use it with the cannon to repair it. Speak to Bill again and he will instruct you how to fire the cannon, and that you will require a fuse, canister and ramrod from the gun locker as well as some gunpowder from the barrel next to the cannon. Use the gunpowder with the cannon, then the ramrod, followed by the canister and then ramrod again, before using the fuse to ready the cannon. Wait until a pirate is in direct aim of the cannon, and then fire it to hit them. If you miss, use the ramrod with the cannon to clean it (or it will blow up and require you to repair it) before adding gunpowder again.
When you have hit one of the pirates, speak to Bill and he will now tell you to sink the enemy ship with cannonballs. Collect 3 cannonballs and fuses from the gun locker below, and then get 3 more pieces of gunpowder. Use the ramrod with the cannon, then add gunpowder and use the ramrod again. Add the cannonball and ram it with the ramrod, adding the fuse and then firing it. You will have to do this three times, however it should be noted that you may miss and will therefore require to get more cannonballs, fuses and gunpowder. When you have hit the enemy ship three times, speak to Bill. The Adventurous will set sail for Mos Le'Harmless, and upon arrival you will see a cutscene. Talk to Bill again to receive an additional 10k reward for your assistance.
Congratulations! Quest Complete!
Guide Made by: DaDa
Corrections submitted by: Dark, Dx1438, Power of Five