This isn't your typical advise for this tame but works great for me. I breed baryonx for caving so I also use them to tame squid, here is how. First of all make sure bary has decent saddle and put him on follow you (and passive). Swim down to squid on bary back and when he grabs bary feed squid then with scuba swim away quickly - preferable toward surface. Dont get so far you cna still see the Bary name plate or he won't be able to follow you.
The squid will drop the bary at a point and they are fast enough to get away from the squid by "following" you after taking not much damage. Wait timer out for feed and repeat. If your bary aren't real high bring more than one. Also swimming toward the surface they will de-aggro the squid.
I tamed most of my squid on Rag.