Sharkigator

Pool Sharks (also called Sharkagators, or Sewer Sharks depending on the location) were biting, amphibious beings that lived in several watery areas.

Variants
There were two different color variant of the sharks.

In the first game, the original dark green color variant was present both in the pools on Umbris and in the oceans on Rilgar. Later in Going Commando, the sharks in the factory on Notak had also the original green color.

In Going Commando, on Notak, the sharks swimming in the ocean had an orange color. Then, from Up Your Arsenal onwards they were always orange.

In Size Matters, the orange sharks that lived on Pokitaru had human-like green pupiled eyes, instead of their glowing yellow eyes in the other games. They also moved differently in Size Matters rather than just moving upwards, turning 180 degrees, and plunging downwards.

Also, in Size Matters, in the beginning part of Dreamtime, the shark's fins could be seen in the water as well as a much larger moving unknown navy blue/purple polygon shape, presumably a larger variant of the shark.

As an environmental threat
Non-attackable sharks were found throughout both the Solana Galaxy and the Bogon Galaxy and were the creatures that ate anyone who decided to swim too far from land. They could be found lurking in the water on any level that does not require the player to swim, making the sharks act as a deterrent for players straying too far from anywhere else in the level besides the set path. On most levels, players could assess whether or not the water was safe; If the water was transparent, Ratchet could swim without being harmed. If he fell in murky water, he would get eaten almost instantly and would be reset to the last Checkpoint. As a prewarning, fins could be seen in the water, however Planet Daxx and Florana in Up Your Arsenal lacked them. After falling in the water, Players were given around five seconds before one of the creatures attacked.

In Size Matters, the sharks also appeared in the Multiplayer map called Island Escape. If a player jumps into the water, he'll get eaten by a shark, followed by a message, "No swimming allowed."

As an enemy
Pool Sharks were encountered as fightable enemies on the outskirts of the end of the level on Umbris that ate Ratchet only if they were in water. These were the only living enemies in the level besides the Blargian Snagglebeast. A few swings of the wrench, or one Hyper-strike, would defeat them with ease. This is the only time as of yet that the Pool Sharks have been attackable.

Behind the scenes
When the sharks attacked, all of the games kept the same "gulping" sound when they ate Ratchet and Clank. This gulping sound was also used in the Pokitaru Infobot from the original Ratchet & Clank.

In the re-imagined series, the sharks were instead known as "Killer Fish".

Trivia

 * The Sewer Shark bares many similarities with the Lurker Shark from the Jak and Daxter universe, as both enemies were used as a way to keep the player from hitting the levels borders by providing a natural deterrent organic to the environment.
 * In Up Your Arsenal, the shark didn't open its mouth when it ate Ratchet.
 * In the Ratchet & Clank Demo, the Pool sharks also didn't open their mouths either, in fact they used exactly the same animation, but in the official release, they did. This means that the "Chomping" animation was eventually scrapped in later games in favour of a simple "Swallow whole" animation.
 * If Ratchet is eaten by a pool shark in Ratchet & Clank: Going Commando; While "in" the shark, if he is attacked by a different enemy, the game will freeze.

Locations

 * Blackwater City, Rilgar
 * Qwark's HQ, Umbris
 * Canal City, Notak
 * Testing Facility, Dobbo
 * Megacorp Armory, Todano
 * Nabla Forest, Florana
 * Research Facility, Daxx
 * Ion Cannon, Koros
 * Jowai Resort, Pokitaru (Size Matters)
 * Dreamtime
 * Island Escape, Pokitaru

Appearances

 * Ratchet & Clank
 * Ratchet & Clank: Going Commando
 * Ratchet & Clank: Up Your Arsenal
 * Ambiguously canon
 * Ratchet & Clank: Size Matters