Complex sentence: They breathe through feather-like gills and are found in bodies of water that do not freeze to the bottom; they are also mostly found in brooks and streams where there is fresh water running, and which have shelter against predators.
Split into simpler sentences: They breathe through feather-like gills and are found in bodies of water that do not freeze to the bottom. They are mostly found in brooks and streams where there is fresh water running, and which have shelter against predators.