This is a resource pack which simply retextures Minecraft's dolphins. Instead of the gray vanilla texture, which was (presumably) inspired by Bottlenose Dolphins, they will now be Common Dolphins, with a vanilla-friendly custom texture.
1.13 to 1.21.11 are currently supported. Support for 26.1 and up is planned, but I will need to create a texture for the new baby dolphins first.
Here's what the pack looks like in-game:
!A Minecraft dolphin, retextured. Instead of gray, it is now black with streaks of tan and white.
And as a bonus, here is a photo of some Common Dolphins in real life:
!Two Common Dolphins jumping out of the ocean waves. They are tan and dark gray, and very graceful-looking.
The above image is in the public domain, and was obtained from Wikimedia.