I think this VN does a near-perfect job - the story is tight and perfectly conveys the MC's declining mental state, the horror and anxiety of being lost at sea while slowly losing yourself is incredibly gripping, and the CG-only style is kept fresh by the large variety of them and the charming line boil effect. I was on the edge of my seat the whole time while reading this, and would wholeheartedly recommend it to anyone looking for something spooky to read!
The one "complaint" I do have is a very subjective one, and also one that is more related to the context of the jam than to the VN itself - while I understand that the characters are in the Bermuda Triangle, I still think the folklore theming is quite weak here. At the end of the day, I don't think the story (and the supernatural shenanigans within it) would lose anything from being set elsewhere - at which point it just starts to feel more like set dressing.
For a story that has so many layers and deep meanings to things, it feels like we're left with somewhat of a surface level interpretation of the folklore theme - and I think it's a shame, because I do think there's stuff to focus on here - Colin's condition of having no reflection is rife for creative interpretations of existing folklore (and in fact, we do see a bit of that, as far as the "vampire" comparisons go), and I think honing in a bit more on those elements, making them clearer to readers, and connecting them more to the central themes of the work could have done it some good in this regard.
Despite me saying all that - the jam theme is basically optional, and I think the VN does an absolutely fantastic job as far as everything else goes - so my recommendation for others to play it stands!