I followed the instructions from Windows Central (https://www.windowscentral.com/how-customize-mob-skin-minecraft-windows-10-edition) for installing a custom mob skin, a manatee to replace dolphins. Everything appears to be correct and I'm able to activate the new resource pack in my world, but I only get the default dolphins, not the manatees my heart longs for.

Would someone kindly tell me what I'm missing?

Thank you.