By far The most usefull dino on the Island map. Tame a pair of 100+ lvl, breed 4 of them, level them up a bit ( 10k hp, 1k meele, and 4k oxigen ) and you can rule the island above and bellow the wather. They are faster than a rex, spend less stamina for running/fighting, and do not use stamina for swimming. Been farming artifact of the cunning ( underwater cave ) with ease, alfa squid of alfa mosa are down in under a minute. Great for farming black pearls, angler fish gel, cnidaria toxin. Nothing can touch them on land eather. What else do one need?
To be strictly honest the spinosaur is one of the best mounts in game if you are even wble to obtain one be sure to make it a high level one they are very squishy at first so go around killing small dinos before attacking big prey
When in water, the spino can move without using stamina, this means that in a fight, if you run into a deep water source, you don't need to worry about stamina if you need to retreat. Has an oxygen bar so you can't dive forever sadly, very fast in water though.