Boss of the Muda Kingdom (World 2) in Super Mario Land. You can find it at the end of the underwater Shooting Area.

Dragonzamasu moves up and down spitting fire and is protected by trusty Tamao. To defeat it, Mario must hit it with 20 torpedoes.

Dragonzamasu looks like a sea horse:
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When Mario defeats Dragonzamasu, you're awarded with 5000 points.