Hi, that sounds like the group called Amphibians. This group includes frogs, most of which start out life as tadpoles that swim in water. As they get older they lose their tails and grow arms and legs. Then they can live on land, although they usually don't get too far away from water.
tadpoles,frogs
Amphibians were the first vertebrates that came out of the water. The first vertebrates that could live outside of the water though were reptiles. or class reptilia this was during the Carboniferous period.
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Whales are an example of an animal with a spine that lives in the sea.
· Quillfish
ox
fish
nice tigers?
Most amphibians are semiaquatic, spending part of their lives in water and part on land.
Anaconda
· Zebra Shark · Zebrafish
seal