I accidentally found something that could be a great speed skip for the sub-shark fight.

You can camp at the very left of the screen and not get hit by the sub-shark. You can get the jelly launcher + ammo, then when the sub-shark goes to the left to do his dash attack, UNLOAD YOUR ENTIRE JAR OF JELLYFISH INTO HIS BUTT. His health will drain VERY quickly, allowing you to kill him VERY quickly. If he somehow survives after you run out of ammo, you can always try to use the tire to butt bounce him, but I think he'd be dead already by the time you run out.

If this WAS already known about, I'm sorry for wasting your time. If you DIDN'T know about it, before, then you're welcome.