California has three beautiful diving regions.

The North coast region is renowned for lush, moist forests of the world's tallest trees, coastal bluffs, secluded coves and wildlife areas. From the pristine beaches and coves of Carmel by the Sea and Monterey Bay, the coastline includes numerous dive locations North of San Francisco, all the way to Mendocino and Crescent City. Each site offers its unique underwater topography and associated marine life.

The California mid region includes diving locations from South of Pt. Lobos State Park (Carmel by the Sea) to Laguna Beach. This long stretch of beautiful beaches can be categorized as open-water diving, with some protected coves and inlets. Capitalizing on optimal weather as well as observing tides and current conditions are crucial to an enjoyable dive experience.

The California South listings include the greater San Diego area (Pt. Loma North to La Jolla) continuing up through Orange County to Laguna Beach. Each ShoreDiving location has unique conditions -- and beauty!

As always, check with your local resources for exact local conditions for the ultimate safe and rewarding dive experience.

California

San Luis Obispo County

Divers will travel far and wide to find the best diving. But those who live in the United States have plenty of great diving on their doorstep as well, with plentiful access to the Atlantic Ocean, the Pacific Ocean and the Gulf of Mexico. From warm-water reefs to temperate seas, here are some of the top places to scuba dive in the United States.

United States

Diving under the pier offers up tons of small marine life. Nudibranchs, sponges, anemones, tunicates, crabs and small fish cover the pilings and bottom. Currents can be extremely strong inside Morro Bay, so plan your dive for slack tide. Visibility can be very poor, so good navigation skills are a must to avoid boat traffic and fishermen.

Check with the Harbor Department office at the pier to let them know you will be diving. They will often allow you access to their dock to avoid a surface swim.

North T-Pier is also known as Morro Bay T-Pier.

Morro Bay

North T-Pier

There are 2 main spurs of rock offshore that are covered with macroalgae and invertebrates. These are separated by a wide sand channel that I have seen halibut, sanddabs, starry flounder and ratfish.
On the rocks there are rockfish, lingcod, cabezon, and kelp greenlings. This can be a very clear dive with 50+ feet of vis, but usually it is less than 10 ft vis. When the swell bumps up there is a milky white precipitate that is just up off the bottom destroying the vis. This is in addition to the sand being lifted up and also ruining the vis.
There are at least 2 big, old style anchors straight out from the beach here. Those are fun to come across.
It is easy to launch a kayak or small boat from the beach here. There are some superb reefs you could access with a small boat.
The dive has an easy entrance and exit, and is great for classes. The spring tends to have the coldest water down to 48degrees. The rest of the year it is usually in the mid 50s. 

Drive into Montana de Oro from Los Osos via Los Osos Valley Road. The beach is a few miles into the park on your right. If you reach the campground, you have gone a little bit too far. 
Plenty of parking in a dirt lot. Outhouse style toilets and picnick tables are the only amenities. Lots of beach goers especially on weekends, but few divers. You will see kayakers launch here, and on a big swell harcore surfers paddle out to the point. 
Short walk from parking area to the waters edge over a sand beach. 
Usually an easy entry with a relatively steep drop-off. I usually put my fins on at the edge of the water and I am floating within a few steps. You should not bother with this spot if there is much swell. 

Spooners Cove is also known as Montana de Oro.

Spooners Cove

This is a small pinnacle that comes up to 23 feet deep from nearly 150 feet on the offshore side. At the widest it is less than 0.2miles wide, so it is easy to miss. Once you spot it on your fish finder you may want to drop a marker so you don't lose it. Wind and swell are frequently problems in this area. 
The pinnacle can have incredible visibility and it is covered in life.
Fish that are common here are: lingcod, cabezon, rockfish(black/yellow, gopher, blues, blacks, olives, kelps, tree, china, vermilion), kelp greenling, sheephead (big ones), gobies, Bathymasterids, and other standard fare.
The entire pinnacle is covered with invertebrates including purple california hydrocoral. 
Amazing for photography.
This is inside the MPA so hunting is 100% off limits. I get checked by wardens about a quarter the time I am out here.
This is an amazing dive! A must see for all divers.  

Boat access only! Launch from Morro Bay and Head South. Or Launch from Port San Luis and head up the coast, giving Diablo Canyon a wide berth (1 mile is required by law). I suppose a true die hard could launch a small boat or kayak from Spooners and get here from there.
The Magic is a dive boat which operates out of Morro Bay and makes special trips out here for small groups (6-pack).

Go to the coordinates and look for the pinnacle on your depth sounder. the spot should be just inshore of the red buoy about 0.2nm.

This is within the Pt Buchon MPA, so leave the pole spears at home.

Buchon Reef is also known as Pt Buchon Reef, Buchon.

Buchon Reef

Jade Cove is an Adventure in all respects!  Plan on making this a full day trek, if not spending the night in the area.  After making an incredibly beautiful drive up (or down) the coast, be prepared for a mild version of Gorilla diving.  The reward?  A souvenir piece of jade to take home to display with your other diving trophies.  There are regulations to be aware of.  A good starting place for web research is <a target="_new" href="http://www.mbnms.nos.noaa.gov/Intro/press_releases/980708.html">here</a>. Getting in at times is accomplished by going under the thick bull kelp that's near shore and has a thick canopy. It's shallow and is affected by heavy surge. In August there is a thick krill layer near the bottom (5ft thick) that decreased the viz to 2-5ft. Beautiful reef, fishes, and if you look carefully you will find pieces of jade.

A rememberence from Daniel S. McDermed:  In 1966 my Dad's hobby was scuba diving, and my grandparents' hobby was making jewlery. In the murky water of Jade Cove, Dad's exploration of a small underwater cave produced a large piece of jade that weighed 17 pounds. I remember a young man offered my Dad 35 dollars a pound for it while my Dad stood there in those chilly waters.  Dad said "Thanks but this man has some real plans for this chunk." Much more than the money offered was gained from the retained stone.

Found 70 miles South of Monterey and 70 miles North of San Luis Obispo, between Gorda and Pacific Valley, on Highway 1. The trail head leading to Jade Cove (Main, Central Jade Cove) is .4 miles south of Plaskett Creek Campground entrance on Cabrillo Highway 1. Free parking on the west side of hwy 1. Walk the straight dirt path to the narrowing switch back trail. There is a spring halfway down with water on the path, the very last leg has an anchored rope line for balance! Cross over some large boulders at the bottom to the cove.

Jade Cove

This spot has a large kelp bed that can be quite thick in the late summer (before the winter storms have ripped it loose). The reef the kelp is attached to has sand channels in between that I have seen sanddabs and halibut lurking. The rocky areas have lots of rockfish (mostly blues, blacks, olives, black/yellows, gophers, kelps), cabezon, lingcod and other regular fare. 
The rocks here are covered in low kelps and invertebrates. Pterogophora understorey with Nereo/macro canopy on top is pretty common. Lots of sea stars, anenomes, and sea cucumbers. Most of the rocks are covered in encrusting invertebrates and small mobile invertebrates, so there is always lots to see. 
In the late spring the young of year rockfish form good sized schools under the kelp canopy.
This area does see some small scale life fish commercial fisherman. They launch their aluminum boats from the beach here and fish from about Lopez Point down to Ragged Point.

This is a beach access spot on a remote stretch of the California coastline. You can pull off hwy 1 into the Mill Creek free day use area. There are bathrooms, barbecues and plenty of parking. The beach is a short walk from the parking area down a small drop-off to an area with cobble and sand to walk on. You follow this around the cliff face to the North (which may be damp at a high tide) to a sandy beach, with large coarse sand. The beach is a steep drop but is easy to access or to launch a small boat or kayak.
Getting here by boat would take a long time, and you would pass better dive spots on your way. 

Mill Creek

Directly off the beach are large sand flats. Look for pipefish and (at night) cusk-eels.  A short underwater swim to the right are low rocky reefs and shelfs.  Giant kelp and gorgonians are plentiful.  Occasionally you'll spot abalone, giant sea bass, and maybe a cormorant.

Drive North from Santa Barbara and Goleta on US 101.  2.8 miles past the entrance to Refugio State Park, make a U-turn at the turnaround, watching of oncoming traffic.  Pull into the turnout on the right.  Look for trains, then cross the tracks and carefully walk to the beach.  Make a careful surf entry.

Tajiguas

It is truly great.  Tgher are many fish and the marine life in the kelp is great.

Drive along Highway one southbound past Gaviota State Park until you reach Refugio state Beach.  Go into the park and park along the beach by the point.  Dive in the kelp beds along the point.

Refugio is also known as rights.

Refugio

If you are lucky, you may be able to see actual oil seeps as well as gas seeps, coming from the ocean floor. The oil seeps look like long black sticks from the ocean floor on calm days. These seeps make up the tar accumulation on the beach.  Not the oil platforms offshore

Park in IV and follow the bike trail down to the beach.

Coal oil point is also known as Deveroux point.

Coal oil point

big scallops and lots of stuff on the rocks

West of Santa Rosa Island

Wilson Rock

Cool reef overhangs, fish in the kelp beds... Great place for a summer-time free dive.

Park on Mesa Lane and lug your gear down the stairs. Enter the water between the kelp beds. If you have a boat, you are stoked...

North T-Pier

Snorkeling and Scuba Diving at North T-Pier