This is quite an early prototype indeed. Gameplay is not here yet, so I will not delve into that too much, but I'd say the concept of a boat and plane hybrid is a nice concept and definitely has potential. If you are going for something cosy I'd say exploration games such as A short hike will be a nice match. Maybe a racing game where you go through hoops around the area? That might be cool.
For the mechanics alone, I'd say the plane controls are a bit difficult, and turning the plane doesn't feel super nice doing so. It may be the fact that so little water is loaded at a given time, and with the simple colour skybox, it's quite hard to tell if you are turning or not. The speed is also a bit problematic (or at least I think), where the ship is basically too slow to be competitive against the plane, which sort of makes ships not attractive to players.
Anyway, with all that said, I do think the prototype works pretty well, and I am excited to see what you can do with it.