Kimmeridge is a great dive site with a boat, or equally a lovely snorkel in the bay can be had on a sunny day.
Heading out of the bay and turning right soon brings you to some amazing diving starting around 6m. Large flat slabs of rock with "cracks", some wide enough to descend into, are revealed. These are often described as the "Kimmeridge Seabed Caves" as some actually allow you to swim below the flat table slabs. These harbour plenty of sealife hiding in the cracks and hollows or small shoals or lobster in the 'caves'.
If you love wildlife, such as this yellow edged polycera ( seaslug - much prettier than the garden variety ) you'll love diving the seabed caves.