What characteristics restrict most amphibians to water?

Most Amphibians must  return to the water in order to
carry out reproduction. They have external fertilization and external development. All
of this takes place in a freshwater environment. Their eggs are not like the amniotic
eggs found in reptiles and birds, with a protective shell. Instead, they are gelatinous
and must be in the water to prevent their drying out. Exceptions are some species that
live in tropical rainforests and lay their eggs with miniature versions of the adult,
which already had the tadpole stage in the egg itself. Although these frogs are able to
reproduce without a body of water, the rainforest itself is moist. These frogs and some
others are the exceptions to the usual Amphibian lifecycle. Another reason they must be
near water is for their skin to remain moist. Their entire body can be used to absorb
oxygen and it must be moist in order to facilitate that. Adult amphibians have lungs but
can also breathe through their moist bodies. It is for these reasons that
most Amphibians never truly conquered the terrestrial environment and don't have the
adaptations to lead a fully terrestrial existence.