[andrewflnr]

What's the selective pressure there? Is it enough that it's less energy intensive than swimming, and their environment lets them get away with it?

[natch]

There’s the reward conferred by being able to get further into shallow areas and take advantage of the additional food options they might offer over and above what’s available in deeper water. Transition zones are abundant with life and thus food.

[pvaldes]

Is a benthic predator, so I would assume stealth.