Normally, sand fleas are not big in size. Most of them measure a half inch up to an inch long. The males grow up to 2 inches long while the females only grow up to ¾ inches long. Sand fleas, also known as mole crabs, have five sets of limbs under their stomach that they use to propel themselves under water. The mole crabs also use their ‘limbs’ to make holes on soft sand. Due to their elusive nature, there are no standards guides on how to catch sand fleas.