Lots of new enemies here! Garyoby is the buzzsaw thing at the bottom, and it moves faster when you land near it like every other enemy of its type. Metall Swim comes with an adorable snorkel and flippers. He'll fire after moving upward, and can sometimes move and shoot twice or move forward before landing. M-422A is the green thing with a claw, which moves downward when you get near it and can't be damaged.
This stage starts off strong, with an upper and lower path that merge into a few jumps over a spike pit. The first fish won't reach Mega Man, but the three following it are all placed to get in the way if we keep moving forward. We can lure them away by inching to the edge of the gap or jumping partway over it, but more impatient players have the option of fighting them directly on the lower path and shooting the last, since it appears sooner and jumps into Mega Man's range.
One more Gyotot appears as we enter the water. The following Metall and M-422As give the player some more minor obstacles to deal with. All the while, the shallow water is messing with Mega Man's jump height as he moves in and out of it. This makes good use of the water physics, gives the player comparatively difficult enemies to avoid, and allows multiple ways to do so.
The next M-422A is placed to give us a scare after exiting the hole, though there's enough room to avoid it by standing still after the hole. Though the deep water makes avoiding the rest of the M-422As easier, big floaty jumps also give Metalls more time to attack, and they now have room for a second shot. The spikes also help make the area seem more dangerous, even if it's unlikely for a player to touch these.
Next up is Moby. He can toss little spiked balls into the water while pulling the player forward, or shoot two missiles from his mouth. The first is easy to avoid as long as we're not standing near the edge of his spike pit. However, his missiles are fast and accurate, and the edge of the spike pit is the only spot safe from these. I always like it when an enemy has a counter for players using what seems to be an easy exploit, though staying near the pit is still safer than trying to dodge the missiles. He takes 14 hits, so he can be destroyed quickly once he leaves an opening.
The next area contain yet more Metalls and M-422As, but the larger spike pits combined with the Met waiting to take advantage of the big jump players will be tempted to make keep this combo interesting for a couple more screens. Players will likely be worn down a bit by now, so Eddie's appearance is welcome.
The brief escape from the water only leads to one Jumbig. Seems like they could have done something more with that. Back in the water, we meet Mantan, who takes two shots and is difficult to hit given his small sprite. He'll move up or down a little based on our position, making himself more vulnerable in the process. The water level also rises and falls at this point, making avoiding all this stuff that much more difficult.
After another Moby and a suspicious hole, we come to the last area of the stage. The water level is changing again, there are spikes floating in it, and Sea Mines are now blocking our path. They drift up and down slowly and explode after we've been near them for a few seconds. This is another good combo, as the Mantans and the movement of the mines can keep a player busy just long enough for one to explode, and a couple near the floor leave just enough space to slide under at times.
That hole leads to a new feature of this game. That is, some levels have a side path leading to a few extra screens. In this case, we get a classic spike drop leading to a new item. I'll cover those later along with the weapons. Collecting the weapon brings us back to the stage's midpoint, which in this case is just after entering the water again.
This one's pretty good. The water is the only real stage gimmick here, but almost every screen presents a new arrangement of obstacles, and the gradual change in enemy pairings gives it a nice flowing momentum. Jumbig once again gets far more space to himself than he deserves, and Moby's missiles are too difficult to dodge without standing under them, but he goes down fast and the two fights with him have some distance between them. While it doesn't do anything drastic to stand out, it's a fun level to run through and provides just enough danger to keep the player alert. The graphics and upbeat music suit it well.