Beach cities in Croatia?

Hello me and a couple of friends are going on an interrail through Europe this summer, we'll probably stop by Croatia, and we're hoping to get a few days at the beach. But as we don't know much about the country, we're at a loss of where to go.

Can anyone reccomend a few coastal cities/towns with an alright beach (and good train connections), would be great if it wasn't a major tourist spot, but we'll take what we get:)