A lightship is a floating ship that acts as a lighthouse to assist and warn other ships in navigation, basically replacement for lighthouse tower.
It anchors in one spot to warn the shipping of such nearby dangers as sandbanks or dangerous currents.
The first lightship in the United States was placed at the Chesapeake Bay in 1820.
Lightships were generally deployed in those areas where the construction of lighthouse towers was not feasible.
The lamp is fitted in such a way that the beam stays steady, even the ship is being tossed by the strong waves.
Lightships also have their name painted on each side, so that during daytime also, other ships can use them to verify their own locations.
Along with a powerful beam of light, some lightships are also equipped with warning bells that can be heard up to the distance of 15 miles (24 km), even if they are submerged 18 feet in the water.
Due to advancements in technologies, the number of lighthouse towers is growing fast and lightships are declining.