COCOA BEACH, Fla. -- Brevard County's most popular beach is crawling with dangerous and disgusting bacteria. Over the past five weeks, four tests have come back positive for fecal bacteria near the Cocoa Beach pier.

Health officials issued a health advisory at the pier, but swimmers didn't even know about it unless they saw one of two signs and bothered to read them.

The last two tests have come back with good water quality, but there is still a mystery about why the water has had higher concentrations of bacteria lately.

Pete Estes sits out on Cocoa Beach near the pier almost every morning, yet he had no idea the health department recently issued an advisory because of high concentrations of fecal bacteria in the water.

"I go in there just to cool off. Yeah, it bothers me. I wasn't aware of that," he said.

Just before Memorial Day weekend, a warning was issued. It was the first time ever for a Brevard County beach. The health department says they changed their warning signs and notified lifeguards on duty, but it alarmed many people Eyewitness News talked to.

"It does make me not so much want to get into the water here," said Connecticut visitor Gary Parker.

Samples of water from the pier have come back with good tests for years, but since May 11 four of ten samples have come back with poor water quality from high levels of fecal bacteria.

Health experts aren't sure what caused the sudden, yet inconsistent, change. They said it could be a higher concentration of swimmers or marine animals. They could not find any problems with the sewer system on the pier and they are asking people to take their own measures.

"Use routine restroom breaks and dispose of their baby diapers in a proper manner," said Cynthia Leckey, Brevard County Health Department.

Every person Eyewitness News talked to said it was the first they heard about it. Some thought the warnings should be publicized more.

"I think they should let people know when it's not safe, so we can make an informed decision whether we want to swim or not," tourist Michelle Lovelace said.

The health department follows federal guidelines and will only issue warnings if two consecutive tests come back with poor water quality and they haven't had that since Memorial Day weekend.