A heavy-lift ship is a vessel designed to move very large loads that cannot be handled by normal ships.
This is the Blue Marlin, a semi-submerging vessels capable of lifting another ship out of the water and transporting it.
Like the USS Cole.
Or, say, a dozen other transport ships.
Or this Oil Rig
Or this one.
This is actually 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 U.S. Defense Department Ballistic Missile Defense System.
And it's huge.
These are drilling rigs with a grid work of iron below them creating a giant footprint to stabilize the weight. They jack up out of the water with those large legs.
And here are three of them.