It's better to tame one you find at a beach/river than one in the swamp. The swamp has a lot of dangers that can make taming in there a nightmare (namely titanboa and other sarco, but leeches are not fun either)
You can find them near pretty much any body of water. Sometimes they are hard to see if they are in the water. They will follow you out of the water, since they are much slower on land try to lead them away from the water.
I just knocked one out. I was very afraid of these monsters before but its actually a quite easy tame! I recommend this snappy thing for beginners underwater mounts. Good luck taming it. [Up so the noobs see ;D]
For beginners, these crocs will make your life on ARK so much easier and you will NOT regret you obtained one. You can ride them at lvl 35. They are super fast swimmers and even travel quickly on land too. To tame quickly:
1 ) Shoot with tranq arrows until unconscious
2 ) Fill it's inventory with Fish Meat or Prime Meat
3 ) Protect your croc from nearby enemies
4 ) Enjoy your new dino !!!!!!!!!!!!
Pro Tip: These guys are great for obtaining tons of meat on land, but bring lots of meat/fish in your crocs inventory before travelling into the water, the croc will eat and drain it's food supply very quickly while underwater. Fish gathering I DO NOT recommend with this dino.
DO NOT listen to the person who wrote the following comment: “DO NOT tame in the lower south cave. It will get stuck on the way out and be trapped there forever.”. If it can’t (which will most likely be the case if tamed down there, because (in my experience) Sarcos struggle just entering the cave with how wide they are. But don’t listen to that guy. Just summon it out in the “Request Creature” tab and wait for it to teleport (I have summoned creatures out of the cave when they get stuck and they teleport just fine). Share this with anyone you know who struggles with that.