Bivalvan

Bivalvan is an Orishan from the Andromeda Galaxy. He was one of the Andromeda Aliens captured by Aggregor. His DNA was put in the Codon Stream and provided Ben with the form of Water Hazard.

History
Bivalvan was first seen in the Fame. Every night he would rise out of the ocean and raid NASA, stealing equipment from their secret rocket project. Ben, Gwen and Kevin attempted to stop him, but Ben couldn't transform because the Ultimatrix detected that his Orishan DNA wasn't in the Codon Stream and went into Sample Mode and sampled his DNA (Bivalvan commented "What did you do?!"), Kevin and Gwen fought him and were beaten. He was working on the damaged escape pod underwater because he wanted to go home.

Ben attempted to fight him without the Ultimatrix, but it didn't work well. Finally, the Ultimatrix finished sampling of his DNA and allowed Ben to transform into Chromastone, who unfortunately, was defeated easily. It was revealed that he stole the rocket's engine this time, which was a nuclear bomb. Tracking him to his underwater cavern hideout, Ben and the others realized he was stealing the rocket parts to repair a spaceship to return to his home planet in the Andromeda Galaxy. However, since he was going to use the nuclear bomb to trigger his launch and destroy Florida, along with thousands of people, Ben and the others had no choice but to stop him. With Gwen and Kevin trapped by Bivalvan's welding torch, Ben had to fight him on his own as Spidermonkey. However, Bivalvan still proved too much for Spidermonkey so he went Ultimate Spidermonkey who quickly defeated him.

Bivalvan then revealed that he and four others (P'andor, Andreas, Galapagus and Ra'ad) were kidnapped by an alien called Aggregor before they escaped to Earth. Ben and the others left him behind while they took the bomb back to NASA, saying they would contact the Plumbers to take Bivalvan home. However, before the Plumbers arrived, Aggregor came, saying that no one escapes him. Bivalvan was then heard screaming off-screen.

Bivalvan reappears in Escape From Aggregor in Galapagus's flashback with a lighter voice alongside Galapagus, P'andor, Ra'ad and Andreas. During his time as a prisoner, Bivalvan seemed not as violent but a leader of the five aliens while having a fierce rivalry with P'andor. He engineered an escape from their cell by using a device he had either assembled while in the cell or had with him while being captured to unlock the cell door and neutralize the device Aggregor had used to nullify their elemental abilities. He also appears to have a natural ability to lead others and make the right decision, as shown on Aggregor's ship.

Upon realizing they weren't in a prison but on a spaceship, Bivalvan realized that they couldn't escape because there was nowhere to go. When Galapagus suggested using Aggregor's transmitter to call for help, Bivalvan approved of it, but P'andor opted to overthrow Aggregor and led Andreas in an attack on the bridge while Bivalvan, Ra'ad, and Galapagus went to the radio room. Unfortunately, P'andor and Andreas's attack alerted Aggregor to the escape of the others and they were all thrown back in their cell just as Galapagus's call was found by Magister Prior Gilhil. The Plumber found them when they were in their cell, only to be attacked and murdered by Aggregor. Bivalvan, P'andor, Andreas and Ra'ad escaped, but Galapagus seemed to betray them in exchange for his own freedom. However, Galapagus revealed that he lied and betrayed Aggregor and his robotic soldiers, impressing Bivalvan (who said "I'm following that guy"). The five aliens stole a shuttle and fled from the ship only to have Aggregor shoot them down and cause them to crash on Earth. Bivalvan opted to stay with the ship as it was their only way off the planet, but P'andor stated they needed to split up. P'andor, Andreas, Galapagus and Ra'ad each went in separate directions while Bivalvan attempted to repair the shuttle through his raids at NASA.

At the end of Andreas’ Fault, Bivalvan is seen in a stasis pod along with Galapagus, P'andor and Andreas.

In Ultimate Aggregor, Bivalvan was possessed to attack Ben's group, though after his headband was removed, he was confused about what happened to him and where he was before being warped back to his capsule. Kevin assumed Max had vaporized him, though he states that Aggregor must had teleported him away. Bivalvan is successfully absorbed by Aggregor at the end of the episode.

As of the end of Absolute Power: Part 2, Bivalvan, as well as the other Andromeda Galaxy Aliens, are back to life after Kevin was turned back to normal.

Ben 10: Ultimate Alien

 * Fame (first appearance)
 * Escape From Aggregor (flashback)
 * Too Hot To Handle (cameo)
 * Andreas’ Fault (cameo)
 * Fused (cameo)
 * Ultimate Aggregor
 * Absolute Power: Part 2 (brief)

Trivia

 * Bivalvan's armor is strong enough to withstand Chromastone's energy attacks and P'andor's heat. This would make Water Hazard one of the more resilient aliens in Ben's collection. This is also proven in Map of Infinity, when Humungousaur angrily beat up Ultimate Aggregor.
 * Bivalvan's voice changes. In Fame, his tone was much deeper with a hint of a watery echo. While in Escape From Aggregor, it sounds younger.
 * In the online game Ultimatrix Unleashed, Bivalvan kept opening his mouth then closing it for 10 seconds then shoots water back and forth.