Kodayake teku ta rabu gida-gida wato kananan teku zuwa kuma manya kamar irinsu tekun atlantika wato Atlantic ocean da kuma tekun maliya wato Red sea kasancewar teku nan ne matattarar duk wani ruwa, ta kunshi manya-manya halittun ruwa kama tun daga kifi zuwa wasu halittu na daban wadanda bamu sansu ba. Bayan haka dandanon ruwan teku yakasance mai gishiri-gishiri ne ba kamar yadda ruwan rijiya yake ba.