There are about 30 species of seals. They all can be classified into
two types: eared seals and true seals. Eared seals have ears that can
be seen, and their flippers work well on land. True seals have tiny ears,
and their flippers work better in the water.
Seals spend much of their time in water. But, they must return to the
surface to breathe, just like other mammals.
A seal's respiratory
system is adapted for water. A seal can go for 40 minutes
without a breath. This allows them to dive to a depth of
over 2,000 feet.
Seals are well designed to swim in water. Their bodies
are very streamlined and their flippers propel them
quickly through the water.