Ahsa

Sea monsters are giant aquatic sea creatures that resemble serpents and live in the methane oceans of Titan. It is unknown if these creatures were always present on Titan, or if they arose or were introduced to the planet following the onset of the Golden Age or even afterward. One creature can be seen through the windows surrounding the arcology's CPU core in the Festering Halls during the missions Utopia and Cayde's Stash. Ghost mentions that the arcology's sensors can detect a large object moving under The Rig, and although the sensors can't determine what it is, this is likely the same creature.

Trivia

 * There is an ongoing debate about . Some claim that the players are mistaking parts of the Arcology's support rigging for a sea monster, much like how in Destiny players thought Batadactyls on Venus were Ahamkara. However, the images about the three "wheels" were taken below the ocean level, an area where the player is not normally supposed to access. This means that the wheels could be a smart solution the 3D artists used to render the monster scaled back while moving from left to right and from above to below the water level, giving a good impression of a sea serpent, supporting the idea of a real living gigantic creature under Titan's ocean.
 * Below the Waves in the mission Utopia and Savathûn's Song (strike), a huge worm-like being can be seen drifting beneath the waves. Its size varies from less than a tenth of the windows, to over half the size of the windows. This could be either due to perspective- the creature swimming at various distances from the windows- or multiple creatures of different sizes swimming past. Its general shape and tail appendages may tell us that this is a monstrous Worm. But until we get a closer look at this creature, its true identity will remain a mystery.
 * If the player were to stand close to Sloane in Siren's Watch, they could hear her mention something below the waves and that it wasn't their imagination.
 * There is a scannable, golden-age terminal on the rig. According to the player's ghost, it was used to scan underwater vessels wanting to dock at the rig. The ghost further explains that the terminal still worked and was picking up something below them of incredible size.
 * Due to the drastic differences in appearance between the "dragon-like" creature that can be seen at Siren's Watch and the "Worm" creature seen during "Utopia" and "Savathûn's Song," it can be assumed that Titan harbors two or even more sea monsters.
 * In The Season of Arrivals there is a voice-line where The Drifter makes reference to "the long boy in the soup" when speaking to Eris Morn, it can be assumed he is talking about the sea monster on Titan.

List of appearances

 * Destiny 2