Hello. I just tried the demo and I must say this is an incredible little game. Its practically a love letter to oldschool N64/PS1 3D Platformers and most blatantly Spyro the Dragon. However as things stand while the design and layout for everything is great and the controls are very intuitive and easy to follow, there's no real challenge beyond finding everything and trying to get that one snail. As others said the underwater controls are a bit clunky. Part of that is because I'm used to propelling by tapping or holding specific button while using the arrow/joystick for aiming, but its not that bad once you adjust to it outside of how slick it feels. I do hope that there will be a way (likely unlockable) to shoot underwater but it isn't necessary if you won't be fighting underwater mobs.
I'm very much looking forward to future updates and the final project. I wish you the best in development on what is clearly a passion project.