Stage 3 starts you right under a Suzy, and rest of this section is a series of drops with Suzys and Mambus. The second screen isn't dangerous, but the Suzys in the third start moving right away, so you have to react quick if you miss the platform. The spray of shots in the last won't hit you if you stand still. It's alright I guess, but I'm getting really tired of these Suzys.
After the drops, the tunnel fills with water and you'll be swept forward just fast enough that walking backward won't quite hold you in place. This could have been a fun change from the norm; having to shoot or avoid things without being able to stop. However, all they did with it was to throw 7 penguins and 10 bombs at you. Each comes in at the same angle and, aside from a short pause between enemy types, the same timing. Jump 17 times to win. That's a shameful waste of a section they made special mechanics for.
This fight never stuck with me much when I replayed this, but it's actually an impressive design for a puzzle boss. Basically, a machine surrounded by a bubble comes out of one of the holes in the wall, moves across the room, then circles it clockwise. It will also fire three shots at you periodically. It takes ten shots to kill one, then a faster one appears. You need to kill seven of them to win.
The catch is, you've got four guts blocks to work with, which can kill one of them outright. However, Mega Man cannot jump high enough to get over one without those blocks, so using them too early takes away your only means (aside from Magnet Beams) of avoiding damage against the later ones. It works on basic enemy mechanics, meaning that you can damage it as fast as you can shoot, but other special weapons won't help much. You can't freeze it, though.
It's an easy fight once you know what's going on since the first three or four are easy to take down with normal shots, and it doesn't deal that much damage. Still, the situation gives you a lot of options to consider in a frantic environment, so it'll seem much harder than it is for the first few tries. I just noticed that the color of the health bar changes with the color of the machine you're fighting, which is a nice touch.