Give in detail, Why must all amphibians spend at least part of their lives in water?

Answer 1

Their eggs don't have a hard shell, so they must lay the eggs in water so they don't dry out (there are a few that lay them on land, but in moist environments). The ones that lay in water have larval forms that have gills for breathing. The gills have to stay wet. There are a few salamanders that retain their gills throughout their lives (axolotls, for one - see photo: http://www.bogleech.com/pkmn-axolotl.jpg ).

Answer 2

because they're amphibians! they are cold blooded creatures, their bodies aren't fit for the dry