Ship's Mage( Stormwrack, p. 93)
You form a potent supernatural bond with a ship. Your spells have a more potent effect when cast aboard this ship. Those spellcasters who possess this feat are greatly favored as ship crew.
Add +1 to the caster level of all spells cast while you are aboard a ship that is familiar to you. In addition, spells you cast while aboard a ship that is familiar to you deal no damage to that ship. It takes one week of living and working aboard a ship to become familiar with it. You can only be familiar with one ship at a time; the familiarity with a particular ship fades should you become familiar with another ship. Additionally, should you remain away from the ship you are familiar with for more than a month, that familiarity fades as well.