I was down there some years ago...a nice resort near Trivandrum before I
headed off to the Maldives.

No diving there, no reefs on the coast there.  Your planned visit is a
terrible time to visit that area -- in the middle of the Southeast Monsoon
which will be raging during your visit.  My visit was early March...birds
in the trees, clear skies...weather not yet too hot...one can stand neck
deep in water and see one's feet and count one's toes.