Hello Steve............
Those holes are the exit current holes of the U-shaped burrows of Tube-Dwelling Polychete Worms. Take the time to dig one out, if you have the energy, you WILL be surprised! Depending on the species and the age of the worm the burrow water current entrance and exit might be three feet or more apart and two or three feet deep. The resident is a segmented worm that might be a foot long and makes excellent bait. I've seen Mexican worm diggers down by El Golfo de Santa Clara using a bicycle tire pump pushed into one end of the burrow then they pump like crazy to blow them out of the other end. Of course they are collected commercially for the ChiCom cave man retard market as an expensive weenie extending delight. How they apply it is something I'd rather not see.
Anyway, the worm burrows are deep enough in the sand to still have water to circulate when the tide is out, they need this for their oxygen requirements and when the tide floods back it is their feeding method. About half of their body is made up of many segmented flap like valves that brings a steady current of water from one end then out the other end. They like many animals on the sand and mud flats feed on small planktonic organisms and algae. They glue the sand along the sides of their burrows with mucus to form a parchment like tube that gives them their other name Parchment Worms. Sometimes after storms you will see them washed up on the beach.
As Roberto mentions above, look for the "pissing in the wind". Not always but sometimes this will be one of several clams that "feel" your foot steps heading their way and do the "squirt" as they pull themselves deeper into the sand or mud. If you can concentrate on the exact spot where the squirt originated you might be rewarded with a nice Razor Clam or the Gulf variety of the Pismo Clam. Again, some serious digging will be required.
Good digging!
JJ
