Caspian Sea
The Caspian has characteristics common to both seas and lakes. It is often listed as the world's largest lake, although it is not a freshwater lake. It contains about 3.5 times more water, by volume, than all five of North America's Great Lakes combined. The Caspian was once part of the Tethys Ocean, but became landlocked about 5.5 million years ago due to plate tectonics. The Volga River (about 80% of the inflow) and the Ural River discharge into the Caspian Sea, but it has no natural outflow other than by evaporation. Thus the Caspian ecosystem is a closed basin, with its own sea level history that is independent of the eustatic level of the world's oceans.
Incat
Most offshore oil rigs are exposed to rough open seas with crew transfers by helicopter and freight needs served by platform supply vessels. However Azerbaijan's offshore oil rigs are in the calmer waters of the Caspian Sea, the world's largest lake, so crew transfers can be comfortably and more economically undertaken by water. Several fast catamarans have been built to transfer both crews and cargo for this market including Incat Hull 074 "Muslim Magomayev" delivered in 2015. The size of catamarans that can be built for this niche market is restricted by the 16.5 metre width of locks on the Volga-Don Canal that connects the Caspian Sea with the Black Sea and the Mediterranean.