The Bases Update or the Seabases Update was a major update, released on Friday, March 13th 2015. It introduced the Seabases, which were major additions. It was a huge milestone in Subnautica Development.
The Bases Update added many of the base modules found in the game today. These include the Corridors, which were new buildable items, and come in different shapes: the X Corridor, T Corridor, L Corridor, and the normal I corridor. These are long tubes, which the player can walk in and build other modules inside. Hatches are needed to enter bases, and serve as doors to get in and out. Ladders are used to access compartments that are built on top of each other, and can be stacked. Windows are used as classic decorations, for viewing the outside environment. Foundations are important, and act as a foundation to a base, and add +2 Hull Integrity.
Lockers were new storage items, which have a large storage compartment inside, and was the primary use of storage, until the later Habitat Update.
The Builder is the tool used to construct bases and their modules. This handy item is crafted at the Fabricator, and is possibly the most important tool in the game.
The Floating Island was also updated, albeit silently. It was updated from a bare, dark landscape to a land thriving with Jungles and Flora. A tweet by Oli Hobbs, a developer of Subnautica announces the development. This was a huge change, and made the Island look like it is today, although excluding the additions of the Abandoned Seabases in the Farming Update, and the Precursor Teleporter Cave in the Precursor Update.
The Bases Update heavily updated the gameplay of Subnautica, and was a huge milestone for it. The Floating Island was also updated to include its iconic Jungle landscape.
The soundtrack's official name is "Precipice".
The YouTube showcase video can be found here: