Note that this feedback is based on the build(s) available at the end of the jam.
There's a bunch of interesting tone at play in Three Ships. The game feels melancholy, but vibrant at the same time. I like the "four rockets and a nudge" aspect and appreciate the way it requires players to get up close and interact with the rocks instead of just shooting them from a distance.
The artwork is simplistic, but is enhanced by small touches like moving clouds and bubbles floating up out of a lava vent. The ukulele music at the end is cute!
The middlemost ship has a rock wedged into it that will carry the ship upward and prevent the game from being completeable if the player doesn't manage to fire a rocket into it before it leaves the screen. Beyond that and some grammatical issues in the title text, the game seems bug-free.
That said, there are a few rough areas that are worth noting. The controls feel a bit too sensitive, and I often found myself accidentally overshooting rocks. A greater feeling of claustrophobia/being enclosed in dangerous waters could be achieved by preventing the the submersible from leaving the water.
The ending comes across as being a little abrupt, and could be made to feel less sudden if progress was counted when a ship reached the surface rather than when a rocket hits a ship.
The atmosphere of the ending suggest a greater connection between the player and the rescued ships/crews than the introductory text indicates. I think that there's room in Three Ships for that narrative to be expanded and explored.
Thanks for submitting and best of luck if you decide to continue development! :D