Just look at those gangly ass toes. T. Rex were floaty mother fuckers that waded through swamps/lakes/rivers and preyed on shit like manatees that were too slow to get away or alligators that were dumb enough to get chomped. The forearms close in close to the body and that bouyant yet powerful tail sloshes it through the water as the webbed feet propelled it. Not very good on land, but incredibly powerful swimmers. I bet they were lazy as fuck though.