Finding this animal can be extremely difficult especially on official servers if you don't have a flyer yet. It's less rare near mountains and metal spawns. One of the most easy places to find one on the Island, is in the middle of redwood.
If you go to herb island then you can find one around 100 as a starter and then just swim it back to base because they are such good swimmers. Makes for a great tame to bait Dino’s and build stone. Easy to tame on herb because of lack of carnos