Hi Leslie,
I can recommend Oahu. I lived there from 90 to 94 and all but a very few dives I made were shore dives. Where depends on the time of the year you are there. The north shore is really nice but not very divable during the winter, hence the surfing competitions held there in December. My favorite two spots on north shore are Sharks Cove and Halieva Trench. During the winter time, we dived mostly at Eternity Beach and Electric Beach. Anyway, there are plenty of very nice dive spots easily accessable by shore. Make sure you have thick soled booties to walk over volcanic rock which can be very sharp.