A scary video has emerged from the US of a swimmer having a close encounter with a shark off the coast of Florida.

The drone footage, captured on Wednesday, shows the predator approaching a woman and then speeding away.

''While filming my girlfriend Helen with my drone a shark came close to tasting her,'' the filmer later wrote online.

''What I think happened was that the shark confused her fins for a fish, but then as soon as it realized it was a human it quickly backed off.''

''The poor water visibility confused the shark. This is how most shark attacks happen in Florida specially this time of year when sharks like the blacktip are migrating through the Florida coast following schools of fish,'' he added.