The undersea cable is an insulating material wrapped wire laid on the sea floor for telecommunications transmission. Modern marine cables use fiber as material to transmit telephone and Internet signals. A submarine cable in the world was laid between England and France in 1850. A submarine cable in China was completed in 1888. There were two cables. One was between Chuanshi Island in Fuzhou and Huwei (Freshwater) in Taiwan. The other was 177 nautical miles long and the other was from Anping in Tainan to Penghu, 53 nautical miles long.

Submarine cable, English name is: SUBMARIEN CABLE, is laid on the seabed and river underwater cables, sub-marine communication cables and submarine power cables. Submarine communication cables are mainly used for communication business, which are expensive, but highly confidential. Submarine power cables are mainly used for underwater transmission of high-power electrical energy, and the role of underground power cables is the same, but the application of different occasions and laying methods. Because the submarine cable project is recognized as a complex and difficult large-scale project by all countries in the world, complex technologies are used in environmental exploration, marine physical investigation, and cable design, manufacture and installation, so there are few submarine cable manufacturers in the world, mainly Norway, Denmark, Japan, Canada, the United States, Britain, France and so on. These countries also provide laying technology in addition to manufacturing.

The submarine communication cable is mainly used in long-distance communication network, usually used between long-distance islands, cross-naval military facilities and other important occasions. The laying distance of submarine power mobile cable is much shorter than that of communication cable. It is mainly used to connect between land and island, across rivers or harbors, and between drilling platforms or platforms from land. In general, submarine cables are undoubtedly more expensive than overhead cables of the same length, but they are often more economical and have more benefits in offshore areas than using small, isolated power stations for regional power generation. In countries with more islands and rivers, such cables are widely used.

Impregnated paper-wrapped cables - suitable for lines of no more than 45 kV AC and no more than 400 kV DC, currently only installed in waters within 500 m deep; self-contained oil-filled cables - suitable for up to 750 kV DC or AC lines.

Because the cable is oil-filled, it can be laid at a depth of 500 m without any difficulty; extruded insulated (cross-linked polyethylene insulation, ethylene-propylene rubber insulation) mobile flat cable - suitable for up to 200 kV AC voltage. Ethylene-propylene rubber (EPDM) is more effective than polyethylene in preventing dendritic phenomena and local leakage of electricity, so that submarine cables can function more effectively; "oil-pressure" tube cables - only suitable for several kilometers long cable systems, because to pull extremely long cables into the pipeline, subject to great mechanical constraints; inflatable (pressure-assisted) cables - use of impregnated paper packs inflatable C-type cables are more suitable for long submarine cable networks than oil-filled ones. However, due to the need to operate at high pressure in deep water, it is difficult to design cables and their accessories, which are generally limited to the depth of 300 m.