The Indian National Centre for Ocean Information Services had issued a warning to States of Kerala, South Tamil Nadu, Puducherry and Lakshadweep.
Swell waves are long-wavelength ocean waves that travel away from their places of origin.
They are usually created by windstorms or other weather systems.
Sea waves otherwise are usually generated due to local winds.
Windstorms and other powerful air current systems transfer energy from the air to water, making swell waves more powerful than locally generated waves.
Because of their high energy, swell waves are able to travel large distances and strike shores with considerably high power.
Swell waves are also called Kallakkadal waves in India, which is a colloquial term used by Kerala fishermen.
The term has now been approved for scientific use by UNESCO.