The three branches of the skill tree (Gunner, Sailor, Plunderer), what each skill does and skill points.
Every level you gain gives you 1 skill point (one for each level after the first). You spend them across three branches; skills belong to you, not your ship, so they add on top of whatever ship and gear you sail with. You can take every point back and spend them again for 50 crystals.
Hunter adds damage against the sea's ships, monsters and fort towers, never against captains. Pirate's Hide is the mirror: it only cuts damage from captains' guns.
Master Mender shortens the repair ability's cooldown: Repair and boost
Seasoned raises the experience from ships you sink; take it early to level faster. Levels and experience
Plunderer and Lucky raise the gold of the loot you pick up and its chance of an extra crystal: Gold and crystals
This page was written from the data of the game's version 1.0.11: the numbers are the game's own.