I'm going to put an end to this myth: The "Giant Submersible Wreck" Easter Egg is most likely just an abandoned underwater research facility/lab. Comparison photo - the Aquarius Reef Base. :
main 1 image - Secret Underwater Base Expansion [.NET] mod for Grand Theft Auto V - Mod DB
The SECRET GTA 5 Underwater Valley You Probably Didn't Know About! - YouTube
Underwater Base - GTA5-Mods.com
What car can go underwater in GTA 5? - Quora
GTA 5 underwater base | <alebal web Blog>
Grand Theft Auto V Hidden Packages Locations Guide - Video Games, Wikis, Cheats, Walkthroughs, Reviews, News & Videos