He is an enormous great white shark with a menacing, battle-worn appearance - jet-black in coloration, retaining the trademark white belly of his species and also having white patches on his fins, complete with heavy scars running down his entire body. He resides in Ciceros Strait, where he enjoys capsizing boats. The title "Lone Shark" can be obtained by focusing on him.
"This enormous great white shark is feared throughout the Aegean Sea, where it is seen as the embodiment of evil and violence.
It actively attacks people and boats and has caused a number of brutal incidents. The many scars on its body are proof of the countless battles it has fought, and its cunning has helped it to evade all human attempts to ensnare it.
This creature is a monster created by ferocious fighting and years of experience which can be seen all over the world, but only rarely."
[ Mother Nature's Revenge? ]
"Normally, a great white shark would not go out of its way to attack humans. Almost all attacks are the result of the shark mistaking the person for a seal or some other creature it considers food. That means shark attacks are rare, only a few each year. But despite this, humans kill thousands of tons of sharks every year to boast, or simply out of pure fear or loathing.
Is the emergence of a creature like Thanatos, which hunts man alone, the revenge of Mother Nature?"
Thanatos makes another appearance in a Notebook quest entitled "Memento", making him the only legendary creature to be featured in both the main story as well as a side-quest. A woman named Marzia asks the player to help her obtain an item from a wrecked ship, the Pride of Athens, the same ship that her father disappeared in when it sunk. Thanatos appears when the two are inspecting the wreck. The player must deter and distract Thanatos until Marzia can open the door to the ship, at which point Thanatos swims away.
Aside from the scene at Triton Village and the Memento quest, Thanatos is found solely within coordinates H-6 and H-7 of Ciceros Strait, near the Wreck of the Emerald Lady. He swims at the same height as the surrounding great white sharks in the area, at a depth of around 75 ft. (23 m).
Additionally, Thanatos can be seen outside of the windows of Valka Castle from time to time, making him the only legendary in the game that can be encountered on more than one map. He cannot interact with the player and does not attack them, preferring to menacingly swim past the windows windows of the Underwater Gallery, the Mermaid's Ballroom, the King's Chamber, and the chamber adjoining the two on the eastern side of the map.
Thanatos spends the majority of his time near the Wreck of the Emerald Lady. He swims around here relatively slowly, cycling in and out of the map (as the only creature in the game to do so) in a circular pattern, with approximately a minute between him leaving and re-entering the map.
Thanatos is highly aggressive and will attempt to attack the player as soon as they swim near him. Thanatos cannot be calmed with the Pulsar, so if spotted, the best course of action to evade him is to swim in unpredictable vertical columns and attempt to make sharp turns. If Thanatos comes near enough, he will slap the player with his tail, removing 2 bars of oxygen from their tank.
His trivia can be gained by taking a picture of him.
- Thanatos appears to be the replacement for Magu Tapa, a different, equally frightening great white shark. Magu Tapa is seen only in Endless Ocean, whereas Thanatos appears to be his replacement for Blue World.
- Thanatos is the name of a Greek deity, the god of Death (not to be confused with Hades, the god of the underworld), son of Nyx (Night) and Erebus (darkness) and the twin of Hypnos (sleep).
- Although it is not stated, it is implied that Thanatos was responsible for the Pride of Athens's sinking and may have thus been responsible for the death of Marzia's father.
- When diving with Hayako Sakurai and watching Thanatos, she says that "He's taken a liking to you...", and that he "Finds you especially delicious."
- Although Thanatos and other sharks do attack the player, they never kill. They do not attack by biting; rather, they lunge at the player and turn sharply, whacking them with their tails. However, no real-life shark aside from the pelagic thresher attacks in this way. This was likely done to retain the game's age rating of PEGI 7 (Europe) / E10+ (America) and to preserve the generally calm and serene atmosphere of the game.
- Thanatos is one of only two creatures who are completely immune to the Pulsar, the other one being the electric eel.
- Thanatos's appearance also closely matches the depiction of the mythical "Black Demon" shark that is rumored to live in the waters of Mexico's Baja Peninsula. The fishermen described it as "A massive shark, anywhere from 20-60 feet long, with dark black coloration, and huge eyes". The large beast is most often seen rapidly rising to the surface, before diving just as quickly, its giant tail whipping wildly, as it disappears to the depths of the sea.
- Thanatos's trivia is most likely implying findings that sharks are slowly evolving to be bigger and more aggressive in response to the environmental pressures that humans impose on them, or perhaps that some Mother Earth-like deity wants to show humans just how dangerous it will become to protect nature.
- Player rumors have circulated stating that Thanatos may be a small megalodon as opposed to a large great white shark. This is likely due to his overwhelming size in comparison to other sharks and his similar coloration, but aside from this, not much evidence is left to support this theory. However, several Lazarus taxa (creatures thought to be extinct) make appearances in Endless Ocean (namely the Sea Serpent, Anomalocaris, and Cameroceras), so while it is neither confirmed nor denied, there is still a possibility that Thanatos may be a juvenile Megalodon or even a tiny adult Megalodon.
- Currently, the most plausible theory set forth uses precise pixel measurements and mathematics to estimate Thanatos's length, which has thus been determined to be 11.4 meters.
- Alternatively, Thanatos could belong to the same fictional genus that Magu Tapa does, Magu. This is backed up by their similar size, appearance, and behavior.
- During his encounter in the "Memento" mission, if the player remains at a certain spot right in front of Marzia, it is actually possible to avoid Thanatos' attacks completely, preventing the need to protect Marzia and making the mission far easier.