Ocean Sunfish Mola mola
Your first awareness of this strange creature often seen on pelagic
trips is a dark fin wobbling back and forth on the surface as shown in
Steve Mirick’s photograph above. Unlike a shark or other fish it doesn't
seem to move forward but rather rocks back and forth with the waves. You
are looking at an Ocean Sunfish or Mola mola. This is one of
the few animals that the announcer may identify by the scientific name
of Mola mola.
Closer scrutiny reveals a large flat fish with a dorsal fin and a
larger ventral or anal fin projecting downward like a centerboard of a
sail boat. There is almost no tail. It is a harmless creature that feeds
primarily on jellyfish and other small plankton. Participants on a
Southern California pelagic trip reported an Ocean Sunfish breaching.