Jurassic Park is a great example of hard scifi in that the problems which happen all happen in believable ways.

It's still fiction and not an attempt to realistically estimate the rate at which problems would happen or the magnitude of those problems if they did. Look to zoos if you want a realistic point of comparison for the risk analysis -- but not if you want to watch a T-Rex chase kids in Jeeps.

Yep. I was actually thinking of zoos as a counterpoint to my post upthread. But the difference is that of scale: how do you allow a T-Rex or a herd of brachiosaurs the square miles they need for their territory and still keep them within that territory? You may as well just say, "let's not bother fencing them in and just use the ocean itself as the barrier."