Interesting little critter. . . . Could be a color variation of the yellow belly sea snake. But those are usually solid black on top and bright yellow on the belly.
I hope we have a resident herpetologist here on CF who can weigh in.
EDIT: I recall
it's CF member
CaptForce who has a herpetology background. . . . If he doesn't stop in here in a day or two, you could message him.