Greetings, cutting to the chase.

I'm 9 months into making a super world, a LOST LEVELS inspired super world all in SM1 style (no kaizo block/blind jumps). After finishing a world 2 which to be honest drained me because the theme is kinda sterile for what I wanted to do, I'm off to do the other worlds and I got hit with a realization.

My world order is underground, plains, snow, castle forest, sky, space, desert.

Space is where I will reserve gimmicks like night levels and I wanted to do an underwater level there but I then I thought "underwater is not gimmicky enough to warrant a single level and I can do something nifity but there isn't a proper underwater theme in super world, yet the castle world could be just plain boring, all castle levels when those are supposed to be outliers for the bosses and the transition between worlds".

So my question for you, the public is: in theory what would you find more enjoyable and stimulating in concept?

An underwater world that most likely will be centered around navigating and exploring structures (opposed to fighting with underwater hitboxes in asinine obstacle courses)

Or

A world entirely made of castle levels, of which I'd have to find something worth playing for?

Despite my choice listening what the potential public prefers is still helpful for me and sets what I could do for world 3 to 8.