I'm not really sure I'm thinking of writing it, but definitely thinking about thinking about writing it
I know, I haven't finished Phoenix, Astroblaster still needs quite a bit of polishing and even Carnival could be improved (let alone the two player co-op version!), but my daughter currently likes Jungle King and I am keen to encourage her retro interests
I'm not sure how I missed it when I went through the early 80s games that hadn't made it to the BBC (or had a disappointing conversion).
Anyway, what do you think?

I reckon some of the horizontal scrolling could be difficult (e.g. in the underwater section), but it's a great choice for a conversion - definitely nice and challenging!

I was thinking of having quite a few small bubbles to give the impression of movement (as the coral doesn't affect game play) and palette swap to make little 4 pixel wide waves skim across the top of the water.

I wonder if you could mode swap 5/1 using vertical rupture which should give enough time to draw the waves.

I think there are issues switching between fast and slow modes and that's why it's never been used.

You might be able to do it with a few blank scanlines after the split but I guess that's not what you're after...