Captains Bane: Hand in for Materials or 900 Contibution Exp + 30 Sailing Exp

Ganined when killing sea monsters, pirate ships, goldmonts, and other enemies of the sea

An addition Similar to 

Hunting: Wildspark

Alchemy: Mysterious Catalyst

Gathering: Fairy's Breath

Cooking: Witches Delicacy

Farming: Blush Leaf

Maybe a nice little minor addition of the sea farers world

I'd say not only from killing sea mobs, but replace the random seaweed and sea water the sailors pick up with this.

Sailor scavengers would be a good addition and add as a byproduct to successful barters too

In addition to the sailing exp/contribution, make other options for exchanges as well:

- riddle-me barter support boxes

- lost trade box (with a random T1-T5 in it)

- crow coins bundles

- random mossy map piece

- ship/carrack gear mats