Cooking Fish in Seawater a waste of time?

According to a new article in Time, "Michael Mina is even going so far as to poach fish in actual seawater at his Vegas restaurant American Fish. ...Michael Mina is even going so far as to poach fish in actual seawater at his Vegas restaurant American Fish. "
But when I take my crabs home, I take seawater with them to boil them in, because it does, in fact, taste better.