Swimming remains off limits as authorities try to determine what washed up on the beach in West Haven Wednesday afternoon.
The substance was dark and dirty and originally thought to be a combination of black algae and sewage, but officials said none of the sewage treatment plants had a release to report.
There was no rainbow sheen to the substance so it wasn't oil. But it's still in the water.
West Haven's Health Director put up signs, signs saying no swimming or wading until further notice. The beach itself is still open.
"It's amazing! This is a beautiful day for the beach," said Gina Valerio. " I didn't come here to swim. I came here to lay out."
She wasn't quite the only one on the sand. After the tide turned there was an odor coming from the water.
"I did notice that," said Patty Gonda. "I just didn't know if it was low tide but I did notice but I was just walking along collecting sea glass."
Deputy Fire Chief Scott Schwartz said tests will determine whether bacterial levels are too high for swimming. He said biologists believe the darkness is seaweed decaying in the heat, nothing dangerous.
"They say it's a natural process. It actually breaks it down and it will turn into a black gooey type in the water that simulates a crude oil leak," Schwartz said.
When the bacterial test comes back then authorities will know whether they can let people back into the water. The incident is not expected to impact the West Haven Savin Rock Festival, which started Thursday afternoon.