I dived with my wife about 10 times before she was certified, she was fine with it, I taught her the basic skills, mask clear, reg recovery, share air. we were diving in BVI, max depth 45 ft, I held her hand litterally the whole time, we had a great time she went on to be an AI. I can no longer recommend it officially however.
Okay, but in your original post you didn't mention anyone (including you) teaching your dad "the basic skills, mask clear, reg recovery, share air." The other poster, @awap, also said he would be happy to take his father diving after giving him some instruction. Your hypothetical was to go diving with your father without him having any instruction beyond whatever he picked up in 1960.