For what it is worth, this is where the level excelled the most. The tileset on top of such a vibrant amount of fish types, which I will get into more detail about later, gave out the right atmosphere. So kudos in this field.
Level Design [2/5]
The points awarded come only from the first section. While ungodly slow, it did teach the player all the types of fish and their respective AI. I found it very appealing that you took the time to create controlled environments for every type of fish, however this is where things start to fall apart.
The level's midpoint is neither before nor after the underwater maze, but rather in the middle of all of it. Meaning, not only are you lost but now every time you respawn you have no idea what is up, down or complete. This is doubled by the fact the level has its own custom boss with no preliminary power-ups to accompany it. Remaining issues rest within "NPC Placement" to reduce redundancy in this review.
Graphical Continuity [5/5]
No issues whatsoever.
Music Continuity [4/5]
While Super Mario Galaxy was very fitting it also hurt you. The level was incredibly slow and tedious, so hearing a musical track that is just as slow as this level is only makes the player feel less ambitious to complete the level. I highly suggest finding something a bit more upbeat to accompany the level's section section.
BGO Placement [5/5]
No issues whatsoever.
NPC Placement [1/5]
I really liked the first section, despite its terrible speed, but the "maze" is what absolutely kills this level's score. There are way too many claustrophobic areas filled with jelectros and fish. On top of this, we have a special fish in the level; yellow fish which are effectively fire-bars. These little guys are placed on a high number causing them to act like roto-disks but on a speed incomparable to Mario's swimming speed. On top of this, there are a handful that don't spawn until after you swim upwards into their "ring" of damage. These elements ultimately hurt you, on top of the maze, and lowered this score significantly.
Difficulty / Replayability [0/5]
The level starts off with an autoscroll set to 1 and then throws you into an underwater maze. This sentence alone makes me never want to play the level again, as much as it pains me to say that. You had a lot of potential in the first section but the fact that it is so slow and then coupled with a MAZE only makes this level tedious on top of being a water level. Sorry. I highly recommend redoing the entirety of the second section to be a more vertical level with the same elements you have available, but on a more reasonable degree of fairness. This will allow you to have a boss in the level at the bottom of a giant water chasm, which will only add onto your chosen atmosphere.
Overall Score: 22/35
Final Score: 6.2/10
Judgement: Pretty Good (Reluctantly, based off Joey's system)