Shelley beach is a sheltered beach in a protected cove to the south end of Manly's surf beach. The walk from South Steyne surf club round to Shelley beach is a quick 15min stop pedestrian walkway that takes you through Cabbage Tree Aquatic reserve.
Stop at the Sea Pool for a dip on the way. The pool is beautiful with a view of the ocean and big enough space for lap swimming. The cabbage tree pool is an ocean pool so don't expect the temperature to be much warmer than the ocean.
Once you're done swimming, continue your walk to find sculptures set in the wall of shells and divers.
Shelly beach (your destination) is fantastic for snorkeling so take some snorkel gear if you have some and follow the rock-line out to the ocean. Just follow the other snorkelers to get a feel of where the best spots are.