Inner meaning of Thrimoorthi

1. Maha Vishnu

He is the God of maintainer. His color is blue. 

This could be the representation of ocean which is in blue color. Evolution started from ocean and everything will end with ocean. With water only the life in the earth is being sustained.

In tamil the Goddess Lakshmi is called alaimagal. (alai means waves)

2. Brahma

He is the God of creator. He sits in the lotus (flower)

This could be the representation of cycle of creation. Because with flowers only everything is being born in the world. 

In Tamil the Goddess saraswathi is called kalaimagal (kalai means art). The creation is beautiful and artistic.

Even the female who attains puberty is called Puppeidhinaal in Tamil, means she has attained the stage of a flower.   

3. Shiva

He is the God of transformer. He sits in hills.

This could be the representation of hills. Because the water from the clouds are transformed through hills only. Transformation of Cloud to water or water from snow etc happen in the hills only.

In tamil the Goddess Parvathi is called malaimagal (malai means hills)

So the water has been given a lot of importance in Hindu mythology.