What is this off the coast?

alien hive

(I'm guessing coral?)

Kelp forest.  It's one, if not the fastest growing plant (algae?) on earth.  It grows up to something like a 1-2 feet per day in ideal conditions.  Anywhere shallow areas along the CA coast where there is a rocky bottom, the kelp will grow.  Little air sacs near the leaves cause the kelp to float up to the surface.  Once reaching the surface, it reaches sunlight and grows even better, forming a dense caonpy.   A forest like the one pictured would be a good habitat for sealife.  Kelp is harvested and the byproducts are used as an emulsifier in several common products like toothpaste, jello, and ice cream.  You probably eat more of it than you realize.

My girlfriend is an amatuer underwater photographer.
The view from underneath:

Looks to me like an algae plume. The Rivermouth in the photo is feeding it. Its that stuff that makes a red tide. Also pollution in water can create ideal conditions by making the water more/less alkaline/basic, warmer/cooler, or by feeding mircro organisms that assist the other algae. Could be a kelp bed, but it has a strange color. Of course it looks very different when paddleing over it on a board.

Quoted: Kelp forest.  It's one, if not the fastest growing plant (algae?) on earth.  It grows up to something like a 1-2 feet per day in ideal conditions.  Anywhere shallow areas along the CA coast where there is a rocky bottom, the kelp will grow.  Little air sacs near the leaves cause the kelp to float up to the surface.  Once reaching the surface, it reaches sunlight and grows even better, forming a dense caonpy.   A forest like the one pictured would be a good habitat for sealife.  Kelp is harvested and the byproducts are used as an emulsifier in several common products like toothpaste, jello, and ice cream.  You probably eat more of it than you realize. My girlfriend is an amatuer underwater photographer. The view from underneath: i43.photobucket.com/albums/e377/mef223/IMAG0059.jpg i43.photobucket.com/albums/e377/mef223/IMAG0082.jpg i43.photobucket.com/albums/e377/mef223/IMAG0115.jpg

  Nice pics.  Makes me want to get back into scuba.  I yousta go to the Channel Islands about once a month.  But that was before kids, job, wife, house, guns.  

Sorry, not a bloom.
Zoom out slightly and look at the smaller clumps.  Isn't it wierd how they appear in two rows of four, in a repeated pattern?  That should have been the real question.

It's a man-made artificial reef preoject.  San Clemente pier is just to the north, and the San Onofre nuke plant is just to the south.  Googled it and found this.

I concur, artificial reef beds, covered with kelp.

I looked at a portion of the map just south-east from there.  I found Wilcox Range aboard MCB Camp Pendleton.  I zoomed all the way in and darn if I didn't find that piece of brass I lost during the last match.