How many times have snake-esque creatures evolved?

I think the theory around carcinisation is neat (crabs do seem really efficient), but there's no way we've seen that type of crabby convergent evolution more often than nature has produced snake-like animals, right? What's more efficient than a tube with a mouth? Eels are definitely along those lines, and really a lot of long sea creatures are. Tons of insects too.

So like I asked, how many different times have we seen nature evolve a long animal that's mostly a wriggling stomach with a face?