Are the beaches of eastern Lake Ontario worth visiting?

There is a good chance that I'll be driving I81 north from Syracuse, NY. I note that there are some beaches on eastern Lake Ontario. Are they worth a visit? Is the swimming likely to be good? What's the likely water temperature? I'm think specifically about Sandy Island Beach and/or Southwick Beach. Some web browsing turned up the fact that Sandy Island Beach was closed due to high bacteria count a few years ago. Is this an isolated incident? or a common occurrence? Are there better options in that area?