Monterey is great above and below water. There is so much beauty and fun there, it is amazing.
There are Art Galleries and the Wharf. It's good for bicycling past gardens that thrive in the
marine air. The best place for a sunset is Pacific Grove.
Because the Monterey area is basically granite, the water usually offers good visibility. Cold upwelling currents blown into Monterey Bay make for lush life. This can make for a plankton bloom in Spring, but Summer and Fall diving is great. There are a few local dive boats that visit the many good offshore dive sites. There is also excellent shore diving including Cannery Row and The beautiful State Park at Point Lobos.
Here are some links to more diving in Monterey.