Toxic Seahorse

Toxic Seahorse, known as Acid Seaforce (アシッド・シーフォース Ashiddo Shīfōsu) in Japan, is a seahorse-based Maverick in Mega Man X3. Under Dr. Doppler's orders, he took control of a large dam to restrict the supply of drinking water for humans.

His body is made of liquid metal, allowing him to sink into the ground and change his position. His weapon is Acid Burst, which releases globs of acid. His weakness is Frost Shield; since the Frost Shield's normal fire delays before launching, it can be used as a trap for Toxic Seahorse.

Mega Man X3 stats

 * Power: 5800rp
 * Speed: 4300rp

Stage name

 * Giant Dam Stage (巨大ダムステージ, from Compendium of Rockman X)

Stage enemies
Enemies in Toxic Seahorse's stage:
 * Sub-boss: Hotareeca
 * Caterkiller
 * Earth Commander
 * Head Gunner customer (before completing Blast Hornet's stage)
 * Head Gunner masspro (after completing Blast Hornet's stage)
 * Mine Tortoise
 * Notor Banger
 * Victoroid

Rockman X3 manga
Toxic Seahorse appears in the Rockman X3 manga, cutting off water to the humans on Dr. Doppler's orders. X and Zero fight him after running afoul of his hidden ambush attacks in the sea. Toxic Seahorse has drowned an entire town, poetically proclaiming it to be "holy ground", upon which our heroes X and Zero should stay away, since it is his "sanctuary". He also ominously says that he is "already dead". They do battle across the town, and eventually come out victorious, forcing Seahorse to flee. When X and Zero follow him, they see he has escaped to the top of a tree, and is quietly hugging the corpse of a frozen, female Reploid, who was his girlfriend. Seahorse is also about to liquefy his programming, which would kill him. X wants to stop him and take him into custody, but Zero convinces him not to, saying they have finished their task of defeating Seahorse and fixing the dam he ruined. Seahorse then perishes, together in death with his beloved.

Archie Comics
Toxic Seahorse is alluded to issue #40 of the Mega Man comic book, when Sigma calls him to handle dismantling the Wily Walker's chemical weapons. He would later appear in Worlds Unite as part of Sigma's Maverick army created to attack the heroes assembled by X, Sonic the Hedgehog, and Mega Man. He and Spiral Pegasus are later seen in the Breath of Fire world trying to set up a Unity Engine only to be defeated by Ryu and his friends.

Trivia

 * The boss fight against Toxic Seahorse is similar in strategy to Toad Man from Mega Man 4. This is because if the player keeps hitting him with an un-charged Frost Shield while he is continuously jumping around, he'll never get a chance to attack. Unlike Toad Man, however, this requires his weakness.
 * Coincidentally, both Toxic Seahorse's and Toad Man's stage take place in a dam.
 * Seahorse does not appear in Mega Man Xtreme 2, a portion of his stage appears in Volt Catfish's Stage. He, along with Blizzard Buffalo, Crush Crawfish, and Gravity Beetle, are the only Mavericks from Mega Man X3 that never appear in the Mega Man Xtreme sub-series.
 * Along with Armored Armadillo and Launch Octopus, this Maverick is misnamed in the Music Gallery in the Mega Man X Legacy Collection. There, he is Acid Seahorse.