The physics mechanics may be awkward and confusing and first, but once you build momentum (literally) you will get the flow of the movement and it feels really satisfying to speed swim through levels. I would suggest adding indicators or arrows at the background to tell you where to go since some parts you are suppose to traverse through land. This is also the perfect game to add a timer to challenge speed runs. Really solid concept for a game.
Viewing post in Wakasagihime Speed Swimming jam comments
The swim feeling was the most important part to me, and I wanted to encourage speeding through more instead of this stop-and-go wandery way I ended up going. I intended to have some time-specific endings as well as a timer at least at the end, but as things are now Sakuya doesn't complain no matter how long you take. XD