ChainD is one of the five apps on chain application in marine environment. ChainD specifically calculates chain length and tensions given the horizontal load at water surface and when the horizontal span is specified. The app solves the catenary curve equations to obtain chain length, horizontal span, and chain tensions. A chain size database is built in the app to allow users to select chain size with ease. Weight of chain, proof load and break load are part of the output. Refer to ChainA, ChainB, ChainC, or ChainE for other scenarios.