First half was alright and aside from the trees sometimes blocking the view from the falling spinies and jumping cheeps I didn't had any problems with it.
On the second half though.
Having to deal with the fishin' boo alone is bothersome since you can't always predict its movement, leading to some unfair hits. This is what makes it so hard to try and design a good level with it, and even though you said you had to be wary of when it was safe, in the end it just didn't make it very fun. A lot of it boiled down to just waiting for enemies to get out of the way, which makes the level feel tedious and longer than what it should be.
Now to be more specific on each path:
Lower path: This one mainly suffered from constantly waiting around for enemies to get out of the way, which coupled with the water physics made it feel slow. Still from what I played it wasn't that bad, and had I tried a couple more times I probably would've beaten it (secret exit though I don't know).
Middle path: This was the only one I actually managed to beat (secret exit included) and even though it sometimes felt claustrophobic it was still manageable at least.
Higher path: Having enemies constantly haunting your ass while also avoiding getting hit by the fishin' boo was annoying and probably is what made this the harder of the three. This was at least toned down on the latest update but the issue is still kinda present.
Also a couple minor stuff:
The block below Morton here is solid for some reason.
The coin below here and the stairs besides it are misleading since thy make it look as if there was ground below.
So yeah i'll say change
Holy shit I spent like an hour and a half on this post
My hacks: Justice for Mario
/ Unnamed Kaizo Hack