From the Super Mario Wiki
Goggley-Blades are enemies usually encountered by Wario in Wario Land 4. They appear in all Passages except for the Entry Passage. They have pectoral fins like fish but appear to have the hind legs and webbed feet of a bird. They wear goggles and have a blade protruding from their forehead.
Goggley-Blades swim slowly across a set pattern, but when Wario enters their sights, they quickly accelerate towards him with rapid speed. They do not change course, so Wario can avoid them by going around them. Wario takes damage should he touch their spear blade. They can be defeated by going under them and hitting their unprotected underbelly.
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