this is my brief analysis of the story so far(chapter 16),may contain minor spoilers,
Story - 5/5
Not a genius idea but it do it very well,reminds me an anime from past year Honzuki no genkokujou,one of the few isekai animes that are worth watching, has a simple idea but fulfills its purpose in the gorgeousness of its simplicity
Stability of updates - 5/5
Dumb thing to exists,take your time to do a great story
World building/background - 4.5/5
One of the most important aspect on a isekai is your world building and The only problem is because for a ocean you can do a lot of a things with it,the ocean has divisions,depending on which ocean you are(pacific,atlantic...) the vegetation and species of animals change,you can give a lot of details for describe the environment,it doesn't have to be credible but there are a lot of things to explore in the ocean,but despite that, the work gives you a very good feeling that the characters are in the ocean and that’s what matters.
Characters - 5/5
For me, the most important element of a story(so I'm going to write more here).I usually think that a story has good characters if you can imagine knowing them in real life or, if not, there is some deep reason behind it,and this work suceeds.
The crab has an explanation in its acts in chapters after its presentation,and the thing that really stands out is the MC,a person with an obsession with knowing how a healthy life works,seeing he discovering new things and the new world and exploring it is simply splendid,the most immersive thing I’ve ever seen in a story until is a character knowing new things,like a manga called Oyasumi Punnpun,a manga that has some of the deepest characters ever created, this manga has its highest points when the protagonist is getting to know the things of life,i felt at some times reading this like I felt reading Punpun,I hope this work reaches the level that was Punpun.
Enjoyment - 5/5
The most important thing when you reading something,this is a very fluid story just go read and enjoy.
Fluid like a wave on ocean.(haha)