The Endeavor | James Boutcher
A science fiction adventure set in the future where a corporation called Mantlecorp colonizes planets to mine resources for a depleted Earth. Elle Cooper, a marine protection activist and pilot of the aquatic ship named the Endeavor, goes on a mission on an ocean filled planet when Mantlecorp discovers they inhabit a planet owned by an alien race called the Onossars. When first contact doesn't go as planned, Elle must convince the underwater alien Onossars and the humans to set aside their differences when the learn they are about to be invaded by another alien race bent on their annihilation.