The color pattern is unusually bright, but that is a juvenile broad-banded water snake (Nerodia fasciata confluens
. Here's a picture with similar coloration (although yours is brighter) - broad-banded watersnake picture
This is definitely NOT a copperhead (Agkistrodon contortrix
)or a water moccasin (Agkistrodon piscivorus
). The head scalation is not correct. Head shape is not correct. Pupil of eye is round. Scales are too weakly keeled. A copperhead or water moccasin this size would have a bright yellow or green tail. Tail shape is not a widely useful character for snake identification.