- Sea horses
- 0.016 kilometre(s) per hour
The slowest moving marine fish are the sea horses (family Syngnathidae) of which there are just over 30 species. Their swimming ability is severely limited by a rigid body structure and, indeed, the only parts which can be moved rapidly are the pectoral fins on either side of the back of the head and the dorsal fin along the back. The major source of propulsion is the wave motion of the dorsal fin: this makes a ripple which drives the fish forward in an erect posture. Some of the smaller species such as the dwarf sea horse (Hippocampus zosterae), which reaches a maximum length of only 4.2 cm (1.7 in), probably never attain speeds of more than 0.016 km/h (0.001 mph). Sea horses are incapable of swimming against the current and, to avoid being swept away, hang on to coral and marine plants with their prehensile tails.