The idol here is believed to be an Agni Pratishta, i.e., with Lord Siva's third eye open.

You can see the pond situated in east direction of the temple in line with the idol, in sree kovil.

It is believed that this is because, the fire( agni) emitting from the idol can be harmful to people.

In order to smoothen that effect the pond is constructed in that way.

This article about Hindu place of worship in Kerala is a stub.