Swimming in Nov on Ishigaki

Hello, I'm planning a family trip to Ishigaki Island in November, and I'm wondering if it will be too cold for snorkeling. I think the adults will be fine, but I have two children, 7 and 11 years old, so I'm not sure about the water temperature. Can you tell me what the swimming and snorkeling conditions are like in Ishigaki Island in November?

by Due_Percentage6438