Looking for some traveling advice. (Madurai to Rameshwaram)

I am traveling to Madurai for three days and want to do a day trip to Rameshwaram. I was looking at trains, and the only option I found was a passenger train that goes to Rameshwaram in the morning and starts from there at 6.00PM back to madurai. This is not the best option as I don't want to wait there till the evening. I wanted to know if there are State run bus services between these two towns and how frequent they are. Looking for some genuine advice on the day trip to Rameshwaram..