Proponents of AAH suggest that many features that distinguish humans from their nearest evolutionary relatives emerged because the ancestors of humans underwent a period when they were adapting to a semiaquatic existence, but returned to terrestrial life before having become fully adapted to the aquatic environment. Variations within the hypothesis suggests these protohumans to have spent time either wading, swimming or diving on the shores of fresh, brackish, alkaline or saline waters, and feeding on littoral resources.[17][18]