If you use a spinosaur to gather bio-toxin do not go into the water, just stay along the shore in quadruped stance, because that gives you more range, the you can kill Cnidaria without them attacking you, a good spot for bio-toxin gathering is carnivore island, it would be dangerous except for the fact nothing on the island attacks a spino, so it is not only a great place for leveling your spino, but also a great place for bio-toxin.