I understand that all the previous tips submitted were useful, but just in case it was not clear, hit the TOP OF THE CRAB, it will have a special animation if you hit it in the correct spot, and will take only a small amount of boulders to tame, even a high level. (Irrelevant with Cannons)
If u want to tame just build a 3×3 stone foundation ang put stone doordrame aroint the foundations exept for the entrace in whick the karkinos will come in and just put a large bear trao ang lure it in and after it will get caught in the vear trap and run around to out a stone dino gat ang badabing bada boom karki os traopes and the rest wll u know what to do catapalut recommended noc cannon
If you want to knock it out with out trapping it have a parcer with a platform saddle it must have at least 2000 health to be safe place the cattpult at the back faceing the back also bring like 15 boulders to be safe and something that you could use to kill one if things get out of control. Lastly you need to make sure there are no alphas nearby in the water because I have encountered a couple before.aim for the abdomen and good luck!
Build taming coral. Lead it in. Build pillers around it until it can't move at all. Build catapult and place up high to shoot down at karkinos. Hit top of body. The karkinos body will move downwards and rebound when hit correctly. Shoot carefully as they die easily. Good luck