A squid-like creature that drifts through underwater stages, homing in on Mario's vertical position. Bloopers move in erratic zigzag patterns — rising toward Mario then darting away — making them difficult to predict. They cannot be stomped underwater.
Swim into them from above to bump them away, or hit them with fireballs if you have Fire Mario (note: fireballs do not work underwater in the original game — bump attacks only). Avoid them by staying at the top or bottom edges of the screen.