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Waterfilter is the second episode of the first season of Ben 10 and the 2nd episode overall.


Ben, Gwen, and Max arrive at Niagara Falls, where Ben is warned not to go into the water, as he can be a little bit 'reckless' in it. Gwen offers to be his 'filter' to tell him when one of his ideas is really terrible. Ben, however, wants to go by his "Ben-tuition" as he believes it can never go wrong. But on Grandpa Max's advice, he reluctantly agrees.

Later that night, Ben sneaks out of the Rustbucket as Cannonbolt and does a cannonball into the water, splashing a nearby fisherman and knocking a rock out of place, waking up a Hydromander. This Hydromander starts 'feeding' by eating everything around it.

The next morning, the din wakes Ben, Gwen and Max up, who see the rampage caused by the Hydromander. Ben decides to fight it using a new alien, Overflow, against Gwen's warning, and is ultimately being defeated. He goes back to the Rustbucket to complain, but meanwhile, the Hydromander finishes its feeding stage.

Ben and Gwen find it laying down, presumably sick, in the water. Ben does a victory dance at this, before its skin bubbles up, and it sinks beneath the waves only to be replaced by more, smaller Hydromanders. Ben, on Gwen's advice transforms into Heatblast to fight them, but he is overpowered by them when they multiply faster than Heatblast can hit them. Also, they pull Heatblast into water, where his powers are useless. Gwen admits her mistake and asks Ben to use his "Ben-tuition".

The Hydromanders are about to crush Ben with a rock, when he dodges and turns into Overflow and starts attacking again. In this time, Gwen discovers that they are weak on land, so she tells Ben to 'do what he always does' and Ben does a huge cannonball into the water, knocking out the Hydromanders from water onto land.

Later, the Hydromanders are locked up and Gwen apologises for doubting Ben, who turns into Cannonbolt and does another cannonball into the water, soaking Gwen and Max, much to their disappointment.

Major Events

Omnitrix Alien Debuts

Character Debuts



Aliens Used


  • It aired as the first episode in U.K.
  • It was added to the Cartoon Network website as a sneak peek on February 22, 2017.
  • The games based on the episode are Power Surge's first level, an Overflow Minigame and a Heatblast minigame.
Ben 10 Reboot Episodes (U.K)
Season 1
WaterfilterThe Ring LeaderThe FilthFreaky Gwen BenTake 10Animo FarmClown CollegeSomething I AteRustbucket RIPBen 24hrsRiding the Storm OutThe ClocktopusGrowing PainsShhh!Brief Career of Lucky GirlAdventures in BabysittingSteam is the WordNeed for SpeedCutting CornersDon't Let the Bass DropVillain TimeBright Lights, Black HeartsRecipe for DisasterAll WetStory, BoredXingoDrive You CrazyHole in 10The Beast InsideTomorrow TodayForgetiScared SillyBad PennyMax to the MaxZombozo-LandDon't Laze Me, BroOmni-Tricked: Part 1Omni-Tricked: Part 2Omni-Tricked: Part 3Omni-Tricked: Part 4
Ben 10 Reboot Episodes (U.S)
Season 1
The FilthWaterfilterThe Ring LeaderRiding the Storm OutThe ClocktopusTake 10Growing PainsShhh!Brief Career of Lucky GirlAnimo FarmClown CollegeAdventures in BabysittingSomething I AteSteam is the WordThe Beast InsideAll WetVillain TimeDrive You CrazyTomorrow TodayStory, BoredHole in 10Recipe for DisasterRustbucket RIPFreaky Gwen BenBen 24hrsBright Lights, Black Hearts
Need for SpeedCutting CornersDon't Let the Bass DropXingoForgetiScared SillyBad PennyMax to the MaxZombozo-LandDon't Laze Me, BroOmni-Tricked: Part 1Omni-Tricked: Part 2Omni-Tricked: Part 3Omni-Tricked: Part 4

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