Rockstar Games is synonymous with easter eggs. There's an entire community of gamers dedicated to looking for anything that Rockstar might have hidden in its games. Some are discovered instantly, while others take years to be found. In this particular case, we're not quite sure yet how long Rockstar has included this easter egg in GTA Online. But, one player appears to have found the Loch Ness Monster in GTA Online.
According to u/Herbzi_Lead from Reddit, there appears to be a likeness of the mythological creature "parked" in the Diamond Casino and Resort's parking lot. The towering creature stands as tall as the street lights and doesn't appear to be moving at all. However, the "weird" appearance of the monster in GTA Online doesn't seem natural. Many of those who've seen the video believe that this is the work of a cheeky modder having a laugh with the game's assets.
If it's any consolation, Rockstar added the Loch Ness Monster to GTA Online before. Players can spot the creature from a distance after fleeing from the Cayo Perico heist. In addition, Submarine helmsman Pavel even refers to the creature as a "friend", suggesting that he might have seen Nessie before during one of his ocean adventures.