You will need a ship that you can put cannons on. Easiest one to get is on the vendor at sea market for around 200k from memory.
Load it up with cannons and the neccessary items (ramrod, swab, charging powder for the cannon type used, cannon balls for the cannon type, fuse cords, match).
Best place to go is jhelom, seems to be lots around there. Say 'start tracking' (kicked myself when I found out that command as I had been sailing aimlessly searching). If there's any ship within 200 tiles you will get an arrow to it.
Shoot the ship with your cannons until it's scuttled while avoiding hits yourself. Once scuttled double click their mooring ropes to board with your pets and go to town. Most of the guys are pretty weak and the captain has a lot of health. Even a weak pet will only need the odd bandage.
Just don't take anything with disarm as I heard they turn into pro boxers.
With low slot pets they will take a while to kill giving plenty of gains