20-74 1/2" (50.8-189.2 cm). A dark, heavy-bodied water snake; broad-based head is noticeably wider than neck. Olive, brown, or black above; patternless or with serrated-edged dark crossbands. Wide light-bordered, dark-brown cheek stripe distinct, obscure, or absent. Head flat-topped; eyes with vertical pupils (not visible from directly above as are eyes of harmless water snakes); facial pit between eye and nostril. Young strongly patterned and bear bright yellow tipped tails. Scale keeled, in 25 rows.
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