Blue Riverbeast

There are 3 tameable creatures with this look.

Blue Riverbeast
Can Be Tamed
10-40Swamplight Trail, Shadowmoon Valley - Draenor
Appear mostly dead, with tentacular growths. Effect is lost upon taming.
Can Be Tamed
10-40The Verdant Mire, Shadowmoon Valley - Draenor
Healthy version.
Can Be Tamed
11-61Ashran (Battleground)
Found on the beach roughly north of Brute's Rise and east of Warspear. It doesn't appear outside the battleground instance.
Level scaling: Most NPCs will scale with the Hunter's level, within the constraints of their level range. Hunters can tame regular NPCs up to 2 levels higher than them, but can only tame elite NPCs of the hunter's level or below.

Matching Mounts

Matching Companion Pets