There are many beaches in Wakayama. However, recommended swiming season ends August. There will be no service in November for swiming.
I checked these sites (in Japanese). Ask hotels or whatever you are going to stay for details.
http://www.jalan.net/theme/beach/wakayama/
http://www.mapple.net/sp_beach/list.asp?PREF=30
https://www.rurubu.com/season/summer....aspx?KenCD=30