This is the Blue Marlin, a semi-submerging vessel capable of lifting another ship out of the water and transporting.
By submerging itself partially underwater, and careful positioning, the Marlin can lift some pretty amazing things straight out of the water.
Like the USS Cole.
Or, say, a dozen other transport ships.
Or this Oil Rig.
This is the SBX-1. The Sea-Based X-Band Radar, which is a floating, self-propelled, mobile active electronically scanned array radar station designed to operate in high winds and heavy seas. It is part of the US Defense Department Ballistic Missile Defense System.
And it’s huge!
These are drilling rigs with a gridwork of iron below them creating a giant footprint to stabilize the weight. They jack up out of the water with those large legs.