Hi there!
I've played it, got to the gold nugget, but nothing really seemed to happen. I tried walking back into the sea to trigger the end state you hinted at but it just gave me another retry.
As far as the content is concerned, the retries are a bit too frequent in my opinion, combined with starting at the surface and slowly sinking down, to then slowly make a little bit of progress before it repeats, makes it feel a bit slow and tedious.
Nevertheless, I am intrigued as to what the end scenario would look like, feel free to give us a hint as to how to achieve it.