The main snorkel spot is Lover's Cove.  I've never snorkeled there,
'cause I'm a diver.  I did snorkel in Catalina when I was a kid, but
only off the main Avalon beach.  I remember getting inked by an
octopus back then, but that's about it.  I didn't use anything more
than a bathing suit, but I was much more cold tolerant in my youth.
There's also snorkeling at the dive park at Casino Point, with
convenient stairs into the water, and you can watch the divers.  The
Casino Building itself is a historic landmark, so at least walk over
that way.  There's a little outdoors bar/cafe right next door that's
pretty good, and if you continue around the point, you hit the beach
club which also has a decent bar/cafe for lunch.

After Labor Day, prices get better and some of the hotels drop their
multi-day requirements.  Still, accomodations are pricey for what you
get.  There are plenty of basic places in Avalon.  Here's one site
that I found in a two-second Yahoo search:
http://www.catalinahotels.com/Catalina_Hotels/catalina_hotels.htm

On that page, I've stayed at the Glenmore Plaza and the St. Lauren -
both are OK, with clean small rooms, only a block up from the main
drag.  The Metropole looks like a real nice place, but they've always
been more than what I wanted to spend.  The last couple times I stayed
on the island, I rented a condo - the first time, in the hills south
of town and the next time, in Hamilton Cove to the north (unless I
have my directions opposite).  The beauty of renting a condo is that
they throw in a golf cart, almost a necessity for diving during the
off-season since the air fill trailer doesn't stay open during the
week and the only other way to get tanks back and forth to Casino
Point is with a cumbersome push cart (or you can "steal" a shopping
cart for Vons, which works a whole lot better than the dive shop
carts, though they're noisy).  Here's a site for the condos:
http://www.catalinavacations.com/.  You really do need a golf cart if
you stay in a condo since it's a pretty long uphill walk from town.
There are a couple of high-end B&Bs that include golf carts as well.
One is the old Wrigley Mansion (the entire island used to be owned by
the Wrigley family), but it's really really pricey.

There's a supermarket in town so you can do your own cooking in a
condo.  I have yet to find a really good restaurant in town, but there
are certainly some edible finds if you keeps your expectations low.
The Busy Bee is great for lunch, since you're right on the water and
they serve prime beef burgers, but their opening hours are pretty
random in the off-season.  El Galleon is good too, for steak, but
they're always out of lobster for some reason.  Nick's Fishmarket
overcooks the mediocre fish.  The pizza place next door is decent, and
has outside seating on the water, but they finally took down the most
exciting thing about the place: decorated dollar bills stuck
everywhere on the walls and ceilings.  My best dining experience was
at the Portofino Restaurant in the hotel of the same name - it's also
a nicer hotel like the Metropole where I'm likely to stay during a
future visit because it's pretty close to Casino Point.

Other than the snorkeling and walking around town, there are island
tours to see the buffalo, flying fish boat trips, glass-bottomed
boats, and even a submarine you can try.  There's not much nightlife
other than a couple seedy bars and movies in the Casino.  I've never
spent more than two nights at a time on the island since I'd probably
end up bored to death, but it's good for a weekend.

snip

did they name the Catalina flying boat after this area?