By Cleve Bryan

WILDWOOD CREST, N.J. (CBS) — Unwelcome guests leave their mark on the Jersey Shore. Jellyfish-like creatures on the sand have beachgoers asking “what the heck is that?”

“They’re a little slimy, a little slippery,” one beachgoer said.

READ MORE: Pennsylvania Gov. Wolf Calls On Lawmakers To Pass Fairness Act, Preventing Discrimination Based On Sexual Orientation, Gender

Call them slippery, call them slimy, just don’t call these clear nickle-sized creatures jellyfish. They’re salps.

“They were slimy, they were a little gross,” Erica Galada said.

Galada took this picture of the large swath of salp Monday morning while jogging on the beach in Wildwood Crest.

Credit: CBS3

Philadelphia Unveils Its First Freestanding Statue Of African American Girl ‘MVP’

“And as I was running, I had to slow down because they were slippery. I thought I was going to fall on them,” Galada said.

Wildwood Crest experienced a salp invasion on Sunday and Monday. So much so that city officials got calls worrying about public safety. Someone even thought a melted glob of them was raw sewage.

READ MORE: Open For Business: Manayunk Chambers Guest House In Manayunk Can Be Anyone's Home Sweet Home

“There was some concerns about that but it’s natural. It’s a natural thing and if you just leave it alone it will just break up and go back in the ocean,” Wildwood Crest Beach Patrol Chief Bud Johnson said.

So what are salps? According to Dr. Christine Thompson from Stockton University’s Marine Science Center, salp are a type of plankton that typically live far out to sea, but float in from time to time with warm water.

Credit: CBS3

WATCH: Surveillance Video Shows SUV Firebombing In Bellmawr

They don’t sting like jellyfish and can actually help swimmers by filtering out algae and other micro-organisms.

“They will float in the water column, they’re called plankton and they filter feed,”  Thompson said. “So they’re a little animal with this jelly coating and they have mesh in them that filters the other plankton from the water.”

Shore official say swimming with the harmless sea creatures is totally fine but be careful not to slip on them.

“They don’t really bother me too much. Well, I don’t particularly like it but I’m OK with it,” Galada said.

MORE NEWS: Former Philadelphia City Council President Anna Verna, 90, Dies

As of Wednesday, the salp have apparently blown out to sea and are no longer in Wildwood Crest.