What tiny critters are likely to bite feet in the Red Sea at Aqaba?

I've just been paddling off of the Kempinski hotel beach in Aqaba, Jordan and got several painful nips! I couldn't see anything that might be doing it and an hour after leaving the water it doesn't hurt and there isn't a swelling so I'm sure they aren't venomous but does anyone know what creatures bite here?

It's something on the sea floor rather than swimming around. The depth is from around 2 to 3 feet (60 - 90 cm approx.) Visibility is clear to the sea bed so anything 1cm or bigger would be visible unless well camouflaged.

Nothing visible on skin at all. Just a very brief pain like an injection with a broad hypodermic needle.