Yeah, Pope's would be a good snorkel site, especially
the sponge garden under the gannet platform...

Popes is a horseshoe shaped annulus, with an internal
depth of 2 meters or so, dropping away to 12-13 on
the outside. "Inside" means within the horseshoe itself.
38'16'36"S  144'41'55"E on google earth

Mornington pier would definitely be worh a look, as
would Rye or Portsea piers and perhaps even Flinders
The cliffs along the esplanade between Mount Martha
and Safety Beach can also be good at times.

If you have access to a boat, South Channel fort may
be worth a look, and the J sub out near Swan Island?
Which is coincidentally on top of another wreck, the
SS. Hersey.

Ian Lewis' book 'Shore Dives of Victoria" might be
worth hunting down, it's probably a little dated now,
but would certainly give you a few ideas...

Cheers

A.L.