The San Francisco Wave Organ.

The Wave Organ is a wave-activated acoustic sculpture located
on a jetty in the San Francisco Bay. The concept was developed
by Peter Richards and was installed in collaboration with
sculptor and master stone mason George Gonzales. . . .

The Wave Organ is located on a jetty that forms the small
Boat Harbor in the Marina district of San Francisco, walking
distance from the Exploratorium. The jetty itself was constructed
with material taken from a demolished cemetery, providing
a wonderful assortment of carved granite and marble, which
was used in the construction of this piece. The installation
includes 25 organ pipes made of PVC and concrete located
at various elevations within the site, allowing for the
rise and fall of the tides. Sound is created by the impact
of waves against the pipe ends and the subsequent movement
of the water in and out of the pipes. The sound heard at
the site is subtle, requiring visitors to become sensitized
to its music, and at the same time to the music of the environment.

It seems to differ from the Sea Organ in Croatia in that it is not a tuned instrument. It projects natural sounds rather than playing chords.