A very good concept! I do like sailing around, requiting allies, gaining new skills, and fighting battles against other crewmates. I would like to see some sort of resource that you use to recruit/learn skills so that you don't just go getting everything from the get go.

Really happy to see a complete battle system created from scratch for this entry! Still plenty of work that can be done to expand the battle gameplay of course, but a quick and easy tweak to improve the gameplay flow would be to move the HP counters and targeting buttons down closer to the enemy/player sprites. Ideally the sprites would be placed over the targeting buttons so that you click directly on them to select the target of attacks and healing abilities.

Also I'm not quite sure how to describe it, but I really liked the wave and water shader used during battles and how the waves were animating so quickly, like it felt like some kind of manic Spongebob diorama made with paper cutouts. If you added just a tiny bit of animation (even just to make them wobble or squirm around slightly) to the enemy/player sprites it would have a really neat cartoony visual effect that would immediately grab people's attention.

A very neat idea, really love the 2D and 3D mix you got goin' on. Pretty bare-boned but the potential is definitely exuding from your attempt. The concept looks like it could be goin' places if you wanted to add some kind of story or something, if it needs it.
Although it's very clear that this isn't 100% finished, the gameplay is fine. The novel idea to have the minigame when attacking seems to work alright, maybe some kind of animation (or when sound gets added) could make it a bit more polished since it's not always apparent if I'm doin' a good job or not. I'm also not TOO sure about what the difference between the Heart and the Bomb even is, even when lookin' at the How To Play. 

Other than that I've found a few 'bugs'/'glitches'----
-When adding Crew members there's no visual update in the top area, only until after get into battle do they appear and after in the open seas on the top.
-The Ship spawns half-way below the waves after finishing a fight most times (still works fine, but visually noticeable).
-One time the Enemy ship spawned zero enemies and therefore got soft-locked, having to restart.
-The Kraken's turn sometimes soft-locks when the two green squares show up and a gray bar that moves up out of the UI, needin' to restart. Although it never happened when I had a full crew, happened the times when I had three characters and only one character.

In conclusion, a pretty intriguing start to a game project that's visually inventive, that with more time in the oven could become something great. Nice job!