Better River is an add-on that will transform river biome into warm ocean. This add-on will add all of the warm ocean component to river biome. So you will see some coral, tropical fish, dolphin (basically everything that you see in warm ocean) in river.
Screenshots
Below are screenshots of better river addon
Notice!
Make sure to turn on all of the experimental gameplay Also, it is recommended to start a new world with this add-on, or the river biome may looks like this if you don't.
