Burst Screen 7, 8 - Crab
Screen 7
Crab Midboss
The crab is surprisingly simple - use Junk Shield. Just stand inside its hit box and pummel it until it's dead.
After defeating it, pause and switch to Rush Coil.
Fast Climb
The Game As Intended
The game intends Mega Man to slowly float up after defeating the midboss. Once the last ceiling spike explodes, the game pushes Mega Man up. This makes Mega Man slowly approach the clear bomb enemies and eventually get to the top to proceed through the stage.
Since the top rises and sinks, it is possible you reach the top at the low end of the cycle and have to wait. Our goal is to avoid that.
The Faster Strat
Your main goal is to be jumping up on the left side when the last spike explodes. This could be a normal jump, or it could be a bounce off Rush Coil.
Jumping off Rush Coil too early can easily Spike Mega Man
Jump from the left side of the room. You have to know how to wiggle through the bombs on the way up, but it's just a small stutter movement to the left. If done correctly, Mega Man should get to the top-top and be able to immediately proceed.
Hitting a bomb will stop your upward momentum and make Mega Man float up at the normal slow speed. The good news is any amount of extra speed is still good.
Get to the next Room
If you are jumping off the high platform, a slide jump (and specifically a slide jump that gets a little extra distance off the ledge) can make it over the spikes. The higher you jump, the more Mega Man plunges in the water, so you will hit the spikes if you miss.
Try to jump past the fish or otherwise damage through them - you need to summon Rush Coil to jump to the ladder, or wait for the tide to float Mega Man high enough to make it.
Screen 8
Step right, then look left and summon Rush Coil.
Use rush Coil to jump to the central pillar. Slide jump (SPECIFICALLY slide jump) to the ladder from here. With the extra distance from the slide, you should be able to reach the ladder. If you fall, try to quickly jump back up to the Yoku block and try again.