Assuming you arrived from the left exit, watch out for the two missiles that approach you. Beyond them, a couple of wheel enemies occupy the next ledge. A combination of these enemies will appear until a ceiling appears at the top of the screen. At that time some floating enemies will appear in both the water and the air. Beyond them are some heat seeking missiles. Jump up the platforms on the right to reach the next screen.
When you reach the top, take out the large hopping enemy before continuing to the right. Watch out for missiles which drop out of the sky when you walk beneath them. You'll encounter a few more large enemies, along with more wheels. Clear each one away as you proceed to the right exit.
