i like it and i think i got some improvement ideas
i think maybe find a way to steer the raft and the bigger your raft the more paddles you'll need. later down the road they could potentially add cyclones, sharp rocks, whales, ect. to avoid by steering away. it would be a unique game mech. huge waves could push things way to fast aswell making it harder to grab stuff sometimes. also a pet you have to take care of aswell could be fun and hard aswell and you can build a cage for it.
difficulty
some more deadly fish good or sometimes two at a time. some creatures i can think about is different types of sharks like a hammerhead, megaladon and others. but other species aswell like piranhas, crabs that can walk on your raft and pinch, birds that will perch before they take food from you, colossal octopuses that can put three tentacles at a time on your raft like old sailor stories, jelly fish so if you jump in the water your injured. maybe rarely a mermaid that will cause mischief or help and a siren that will sing and make you want so swim away from your raft. they all could have different personalities and come at different times, weathers or locations. i think your health could need like bandages or meds or morphine to stop bleeding and heal. also more bars for like having to pee (we do drink alot of water lol) or being to hot and cold.
aesthetic
i think maybe it could use more aesthetic like weather changes snow, glaring sun,rain, foggy that could be cool and they could effect you too (if its hot stand in the shade, if its cold stand close by fire, if its foggy it could make it harder to see and maybe get a rain catcher? idk)scenic things too like dolphins jumping by or a huge whale off in the distance blowing water, shooting stars at night, flying fish. aswell as scary scenery like a bitten corpse, dead fish all bellied up, oil spills, a huge tentacle waving in the distance. you could see ufos off in the distance but one night you hear weird noises so you go outside and see a ufo beaming a whale and bringing it up and over your raft as huge amounts of water are dripping ontop of you. the whale... wailing! you hear engines and they both suddenly disappear..... or you know you could add decorations potted plants with flowers, art, telescopes,a hula girl dash bobble thing ect. and a way to upgrade your raft maybe start off wood but transition into metal and eventually make your raft more boss with radars, harpoon guns, canons and electricity so it feels progressive. the barrels could also be crates and they could carry man made stuff like decorations.
i hope i helped a bit