Here's a rundown on the possible shore dives around Manzanillo. Also after reading it you'll understand why there's not much talk about shore dives in Manzanillo.
San Peditro: Is a beach near downtown Manzanillo. It is a possible dive site along the Jetty, although I can't tell you how good it would be. I haven't been there myself. Also you would end up carrying your gear quite a ways. There can also be quite a bit of fisherman in the area depending on the time of the day. Unfortunately the local fisherman don't understand what a dive flag or a safety tube is, and they don't care. I have a friend that has had fisherman casting lures at him while he was snorkeling in the area.
Las Brisas Jetty: It's on the other side of the port entrance from San Peditro. There are quite a bit of fish that hang around there. But because of that there's the same warning about fisherman also. In addition the port has been expanding and dredging so the last time I was there it was what is described as chocolate diving. 3-5 foot visibility.
Club de Yates: This has to be the best shore dive around Manzanillo. It is placed out on the Santiago Peninsula. The area is in a V shape with rocks on both sides, and a nice rock formation about 300' out that is easy to swim to. The bottom is 15-25 feet if you stay closer or down to 50 feet if you go out to the rock formation. This is where some of the local divers take the majority of their underwater pictures since it's an easy and nice dive. The problem with this place is there's a condo going up that's trying to privatize the access or the parking area, it's not known which yet since they won't tell anyone. So it is possible that come February there may not be access to the beach anymore.
La Audiencia: This is a beach also on the Santiago Peninsula. There is public access and it is a very popular beach. Because of this there are a lot of people and a lot of boat/jet ski traffic in and out of the bay. If you are up for a little swim you can get to Club de Yates from here. I haven't been diving here myself because of the traffic.
San Luciano Shipwreck, La Boquita: La Boquita is populated by quite a few restaraunts but there is still plenty of parking. The ship wreck is about a 300 foot swim from shore. Depending on the time of the day I would suggest swimming out underwater to avoid boat traffic. Visibility can be from 5-20' with a sand bottom all around the wreck. I'd suggest a flashlight also to shine into the crevices. There have been octopus, seahorses, and sea turtles seen there along with many other fish including a lot of curious balloonfish, spotted boxfish and spotted sharpnose puffers.
L'Recif: This is listed as a shore dive on several sites. I haven't been here and the reason most people can't get here is it's private. Well, the beach isn't if you get there from the ocean but a large area of land around the beach is private. We've been denied access and unless you know someone that lives in the community there you'll probably be denied as well.
Barra de Navidad / Melaque area: This is a big bay about a hour drive north of Manzanillo. I haven't been diving there and I have limited experience in the area. There may be some shore options up here. I have some friends that are moving to the area later this year and they'll know more about shore and dive options up there.
Tenacatita: This is an area that's about a 90-120 minute drive north of Manzanillo. It's a nice area to snorkel and I've heard there's some good shore diving there also. There currently is a small dive shop there that you could get tanks filled at.
So as you can see there's one, maybe two good shore options without a long drive in Manzanillo. Although this shouldn't discourage you from diving in the area. Manzanillo is a great place to dive and there are a lot of places to go from boat. There's a great diversity of fish and some beautiful rock structures to swim through.
Now I do partially own one of the shops in Manzanillo. But you don't have to go diving with a shop. As a certified diver you could find a guy with a boat and go out on your own if you wanted to. I'm also not trying to steer you to boat diving. The above sites and descriptions are just what I've found in the area. There's a lot of lovely beach area but there's not many spots that are good for diving.
LoboMX