This addon includes mobs which are expected to be released in the Aquatic Update. The designs featured in this post are just concepts and should not be seen as official. However, they should be somewhat similar seeing as they are based on art provided by Mojang. The new features are kelp, dolphins, fish entities and four other mobs.
How does it work?
All of the new things (even Kelp which looks similar to blocks) are actually replaced entities/mobs. They are fan-created concepts and should not be viewed as anything official.
Kelp: Kelp is the name of the mob which can be used for spawning spawn a wide variety of underwater ocean plants. Make sure to aim straight down at the ground to spawn them as otherwise there is a risk it won’t spawn as intended.
Dolphin: The Dolphin is a new mob which can be spawned underwater by the use of a spawn egg or by using the /summon command.
Fish: Some ordinary land mobs have been replaced by fish which are new entities you can use spawn eggs to spawn underwater. You can use a fishing rod to catch the new items. The fish will go after the fishing hook and die a few seconds after.
The Monster of the Ocean Depths: This mob is a replacement for the squids. (It didn’t make it into the update.)
The Great Hunger: A mob which is constantly hungry (and hostile)? (It didn’t make it into the update.) You won’t see it if you try to spawn it in creative mode as it will quickly turn invisible. Switch to survival mode and it will quickly start attacking you.
The Hovering Inferno: A pretty cool (most likely) Nether creature which didn’t make it into the update.
The Monster of the Night Skies: This is Mob B and also the one which got the most votes during Minecon which means it will be the next mob added to Minecraft. Remember, this addon is just a concept so it will most likely look different from what you see on the image.