A Texan company has designed a 22,500-ton oil exploration ship that splits in two so it can go down the narrow canals to the Caspian Sea. Exmar Offshore was commissioned by oil company Conoco to find a way of getting an oil rig into the vast landlocked salt-water lake.

Conoco asked Exmar to design a complex weather-beating semi-submersible exploration rig that could be built, cut up and transported by barge to the Caspian. Exmar looked at the local weather and thought a simpler design of split ship would withstand the north-south Caspian storms.

Split ships are not unknown. Split hopper dredgers in Holland sail with cargo holds of gravel and dirt and have hinges on the top of the deck. The whole boat opens like a clamshell, dropping the spoil, and then the boat, which has sunk, floats to the surface.

Just four bolts (tensioned members with threaded end caps) hold the Sturgeon together. The ship's accommodation block and drilling tower will be mounted on sliding foundation pads that are intended to absorb flexing of the assembled boat. The Sturgeon design is ready and the company is patenting the idea.