Level 400 is the 401st level of the Backrooms.

Level 400, more commonly known as "The Ocean of the Final Frontier", is an infinite ocean, with a presumably infinite depth. Level 400 contains several anomalous properties, in addition to several forms of biological life which can be encountered in the several parts of Level 400, these parts being The Depths, Near Shore, and a currently unconfirmed part known as Silver Waters. After every four hours, a thick mist will begin to form, and a lighthouse can be spotted, shining a bright yellow light, however, it is not possible to reach and will remain at the end of a wanderer's sightline at all times, once five hours have passed, the mist will begin to dissipate and the lighthouse will disappear from view.

An image of The Depth's waters.

The Depths is a presumably infinite ocean of unnaturally dark and choppy water, the sky of which is grey, with an unknown light source as no sun can be spotted within the sky. Due to the infinite nature of the ocean, The Depths causes rapid sanity-draining effects, resulting in wanderers turning into Wretches. The Depths is the largest of the several parts contained within Level 400 and is where any and all wanderers will arrive upon no clipping into the level. Swimming deeper into the ocean will cause the sanity-draining effect to become far more pronounced, though if one is able to withstand this they may encounter specks of white light always seen from afar which cannot be reached, which will grow in numbers the further one travels. Several presumably man-made ships can be found suspended within the deeper waters of The Depths, the entry of which will reveal that the ship uses technology far more advanced than what is currently within human capabilities, the origin of these ships is not known. It is believed that The Depths have an infinite depth, this cannot be confirmed however, as the water within The Depths is unusually dense, causing the pressure to rise very quickly the further one swims down.

A highly aggressive entity residing in The Depths. Death Whales resemble the common Humpback Whale which can be found inside The Frontrooms, though they act nothing alike, and Death Whales are in a notably greater number, being that one can be found for every two miles in the vast ocean. Death Whales can detect nearby wanderers and will swim under them at varying depths, once they are close enough they will attempt to swim directly upwards as if they were intending to breach the surface of the water, swallowing the wanderer whole.

An image of a Death Whale narrowly missing a wanderer Ocean Explorers who was unaware they were being attacked.

Death Whales are notably faster than Humpback Whales, so one should prioritize leaving this section of the level as soon as possible, and swim to safety. Death Whales will swim upwards at a speed such as to breach the surface, if they do not successfully consume the wanderer they will breach the water, and attempt to swallow the wanderer swimming downwards at rapid speeds upon re-entry of the water. It is of great challenge to know when a Death Whales is underneath a wanderer, as they give little to know warning and may attack at any moment. Death Whales can often be seen with their mouths gaping open and protruding from the water, it is believed that Death Whales breathe through their mouths and that this is in fact a Death Whale consuming oxygen before resubmerging. As of September 9th, 2023, fifty-six deaths have been reported due to Death Whales. Death Whales are solitary hunters and it is rare to see more than four within the same region.

Near Shore is the second section of Level 400, and is relatively safer than the first section, The Depths. The second part of Level 400, a greatly safter section than the murky waters of The Depths

An image of the rock formations in Near Shore.

Upon swimming far enough into Level 400, one will eventually arrive at an area that appears to be a shoreline, though no shoreline is ever visible despite how far one may travel, this section is known as Near Shore, the furthest reported travel into Near Shore that has been documented is twenty-six miles, traveled by two members of M.E.G., before turning back due to the risk of starvation. Black rocky formations can be seen throughout Near Shore, as well as a large surplus of various kinds of sea life. The sky within Near Shore is notably brighter than the skies of The Depths, though it still maintains a grey coloration, the water contains a much brighter tint, and the drastic sanity-draining effects of The Depths are no longer present.

Many distinct types of fauna can be seen within Near Shore, both native and non-native.

Silver Waters is a highly rare section of Level 400. The Silver Waters consist of a large sea with metallic water, maintaining an unnatural texture, the skies of this section are pure white and may cause eye strain. Chemical analysis of the Silver Waters shows the composition to be that of liquid silver, though the water maintains no notable difference in temperature. Silver dolphins are rumored to inhabit this section of Level 400 though they have not been properly documented as of yet. The method of entry into the Silver Waters is not fully known as many arrive at the Silver Waters purely by accident, though it is thought swimming far enough into the Near Shore section will lead here. The Silver Waters have an undetermined depth as attempting to dive down will give the illusion of making distance downwards, once one attempts to swim up they will realize they have been right below the water surface the entire time.

The only image ever taken of La Kameloha.

A large stone humanoid of unknown origin known as La Kameloha, named by The Nokenoke, believed to be the only one of its species. Little is known about La Kameloha though it is thought to be around 100ft tall and is generally non-hostile, having only killed two people via grabbing them and attempting to take them under the water, where they promptly drowned.

Currently three colonies/outposts exist within Level 400, and although the M.E.G. frequently explores this level, they currently have no outposts within the level.

The only official group known to be stationed within the level. They welcome newcomers and help them with egress from this level. They appear to enjoy living within Level 400, often stating that "we are happy where we are". They live on a giant inflatable raft and travel between sections, and enjoy partaking in swimming

A recently discovered tribe of about fifty island tribal people on an island in Near Shore. Not much is known about them but they have a stable economy and a hunter-gatherer society. They are somewhat hostile to wanderers, though no known fatalities have been reported to be caused by them.

A small detachment of the Imperial Saudinian Royal Navy located on one of the larger islands in Near Shore that has been expanded artificially and made into a naval base in the style of Pearl Harbor. The ISRN unit consists of five Atlas-Class Automated Destroyers, one Arrakon-Class Cruiser and eighteen Shvirk-Class Frigates, though none of these ships have ventured far from the base.