Cpl. Brandon Embrey, of St. Augustine Police was one of the first to find these creepy crawlers, and he said he couldn't believe his eyes.
"There had to be millions of them, I couldn't see the bottom. All I could see was red," said Embrey.
Embrey also said they started to disappear because mullet were attacking them.
Dr. Quinton White, a professor of marine biologist at Jacksonville University, saw the video from Vilano Beach and said it was a classic bristleworm mating frenzy. He said it happens every year when salt water warms up.
Video: Thousands Of Bristle Worms Seen
Bristleworms range in size from about 1-inch long up to about 20 inches in length. Most small ones are an orange color, but occasionally appear two-tone in color.
Larger bristleworms are frequently gray or brownish in color. Bristle worms are composed of many segments and have bristles (setae) which extend from both sides of its body along its entire length, hence their common name.
Bristleworms live in the sand or within the live rock. They are nocturnal and not usually seen during the day.
Historically, bristle worms were all considered to be bad. Most literature warns that they can attack and eat clams, anemones, corals and even fish.