Gamers typically enjoy experiences in which they have the freedom to experiment and tackle situations based on their own decisions, and this is why The Legend of Zelda: Breath of the Wild was such a success. It has redefined open-world games ever since its release with revolutionary new mechanics like gliding and climbing, and multiple successful games have since taken these ideas and expanded upon them in their own worlds - like how Immortals Feynx Rising added underwater segments to its BOTW-style gameplay. Ironically enough, Breath of the Wild had some unused underwater ideas Breath of the Wild 2 might implement instead.
Breath of the Wild shook up The Legend of Zelda's formula by removing the linear restrictions of the previous installments. Players genuinely enjoyed the ability to route out a path through the map entirely on their own, but they also enjoyed how much freedom they had with its lengthy list of activities. With the inclusion of climbing, gliding, cooking, and even riding on random animals, Breath of the Wild incorporated lots of options for players to interact with the environment. However, it was strange to see how limited the swimming mechanics of Breath of the Wild were.
DidYouKnowGaming? posted a video on YouTube that detailed how Nintendo had plans to include underwater segments in Breath of the Wild. In most of the 3D Zelda games, it was possible to submerge beneath the surface of the water, and multiple areas and dungeons took place at least partially underwater. Majora's Mask and Twilight Princess even included new abilities for Link that made him particularly mobile underwater. Breath of the Wild might have expanded Link's options outside of the water, but this game has one of Link's most limited swimming move sets since Wind Waker. However, the developers' plans to create underwater sections in Breath of the Wild could still end up in BOTW 2.
How Nintendo Could Implement Underwater Content In Breath Of The Wild 2
In Breath of the Wild, there's a glitch in Lurelin Village that lets the player see beneath the opaque surface of the ocean, and this reveals a vast array of coral reefs and fish that cannot be seen otherwise. This insinuates that at some point in development, players were able to dive underneath the waves like in previous Zelda games, which could have been very interesting in Breath of the Wild.
Perhaps in BOTW 2, players could be able to explore underwater caves filled with sea monsters to fight and loot to collect. There could be a collection of air pockets or even simply bubbles that replenish one's oxygen supply so that it isn't necessary to resurface constantly. Breath of the Wild's fishing could also be expanded on, since players could chase Hyrule's aquatic life deep into the drink. To add to this, players should be able to take pictures underwater, so Nintendo can add more of those sea creatures to the Hyrule Compendium.
By extension, there could even be something as important as a Divine Beast located underwater. It's unknown what kind of dungeons might show up in Breath of the Wild 2, but it could be awesome to navigate a dungeon entirely submerged in water. To encourage the freedom that comes with this new style of Zelda, perhaps players would still have access to their runes while underwater, which could lead to engaging puzzles and unique combat encounters alike.
For example, there could be unique jellyfish guardians that fight with original attacks and force Link to take advantage of his underwater mobility to dodge and counter-attack with the proper rune. Beyond that, the developers could include segments where Link might need to alter the current in the water, or perhaps even the temperature (with his Cryonis Rune, for example). Breath of the Wild clearly had a lot of innovative ideas that shook the industry, but it's also clear that the game's unused ideas could have a strong impact on the quality of BOTW 2.