You may be intimidated by their large size, but wild Spinos honestly won't attack you as long as you don't get to close. They have a very close range of detection for food, but once they do see you, they will follow you for a long time. They also tend to run in large circles and change direction when you are trying to shoot them. That's not such a big deal though since their are no multipliers for headshots on a Spino. Finally, a Spino will move faster in the water than you or most dinos that aren't a sarco. So running to the water to try and lose them isn't very viable.
I had a spino named Bubbles. He max level (150) and a BEAST. I think he had maybe 30,000 health. He was so loyal, and so brave. Until it all went down...
Me and Bubbles were out hunting for EXP for my otter, Nibbles. We found two mated rexes, and attacked. We easily killed them both, and Nibbles got plenty of experience. Once we returned to the base, my tribemate was going insane, screaming. I raced over, still mounted on Bubbles, and asked what was happening. “We’re being raided!” He shouted in a horrified fashion. I immediately turned and raced out on Bubbles. He fought to his last breath, his last attack being driving a giga away from out argy, Toriel (#PrayForToriel). Sadly, Bubbles didn’t make it. But that act of bravery and his fearsome fighting won us that battle. So now, comrades, remember to appreciate your tames. They may eventually die, defending you loyally.
If you are having a hard time finding spino's in their respective spawn zones (especially Ragnarok), kill all the fish in that area. They share the same spawn capacity and can be out spawned by coles! ( up vote so Rag players know!!!)