Thank you so much for your words Valeriy, they mean so much to me after all the work i've put into these jam days. Of course it could be a better game, as always, and with the time (or lack of it) being a huge constrain. If you would like to suggest ideas to convey the theme of the game more through AV elements and so make a better game, I'd genuinely love to read them! Huge thanks.
I think that the easiest and most effective way would be to add sound effects that would reflect escalation of the events. I.e., tense silience as the boat rides with its normal speed can change into nervos chatter, accompanied by the dying engine hiccups, then turn into indiscriminate shouts and screams, as the situation worsens. Soundscape is very important in your game as it is at establishing sense of place, and it can do more to enhance player's sense of presence at the scene.
On the visual side I would stay minimalistic, but maybe add some visual detail to indicate boat's state as it stops (maybe, smoke coming out of the boat?)