mˈɛni spˈiːsiːz ɑːɹ spˈɛʃəlˌaɪzd fɔːɹ lˈaɪf ɪnðə dˈiːp mˈoːɹ ðɐn swˈɪftli mˈuːvɪŋ wˈɔːɾɚz ʌv lˈɑːɹdʒ ɹˈɪvɚ tʃˈænəlz, lˈaɪk ðæt ʌvðɪ ˈæmɐzˌɑːn ænd ɪts mˈeɪdʒɚ tɹˈɪbjuːtˌɛɹiz wˌɛɹ ðeɪ hɐvbɪn əbzˈɜːvd swˈɪmɪŋ vˈɜːɾɪkli.
Many species are specialized for life in the deep (more than ) swiftly moving waters of large river channels, like that of the Amazon and its major tributaries where they have been observed swimming vertically.