The rule of thumb at the shore is...  
there's more here than meets the eye.  The water itself contains life of all kinds, shellfish and anemones cling to rocks, tiny crabs burrow under the sand and wait for the tides to bring nutrients.  These pictures focus on the life I've discovered on exposed rocks at low tide.

 

A colony of goose barnacles, which have positioned themselves to catch the water run-off from their rocky home

Mussels and sea stars emerge--well, partially, at
least--from their underwater home at low tide. 

A sea star clings to Alex's rock, surrounded
by a colony of tiny anemones.  The stars have
a firm but thin exoskeleton.  If you touch them
gently, you can feel their soft interior.

Anemone colony.  Sand-colored at low tide,
they open their tentacles into flower-shaped
glory underwater.  The mouths of the large ones
here are about 1 1/2 inches across; the smaller
ones, about half an inch.

A typical array of sea life greets the daylight at low tide: mussels, sea stars, anemones and goose barnacles.

A two-inch-long chiton clings to a rock between two mussels.  Don't try prying them off; these guys have cornered the market on adhesion.