This is the nerve-wracking moment a fearless snail rested on top of a pit viper's neck.

The oblivious mollusc was seen perched on the bright green Wagler's Pit Viper following a downpour of rain in Singapore on March 6.

It had crawled over the serpent's neck while the predator remained motionless on a wire fence.

The viper flicked its tongue out occasionally, but did not seem to mind the slimy creature intruding on its personal space.

Wagler's Pit Vipers are relatively docile and small snakes that usually grow up to three feet in length. They tend to be sluggish during the day, being nocturnal arboreal hunters that prey on lizards, birds, and rats.

Despite their mild demeanour, their vividly coloured scales indicate the deadly venom they carry.