Gum failed the first phase of BUD/S, but he was granted permission to return to training for a second time after senior leaders saw he had viral gastroenteritis. Gum again went through the first phase of BUD/S, but again he went to medical, where tests showed that his "blood came back toxic" from rhabdomyolysis.

The SEAL was put on medical leave and able to fully recover in his home state of Pennsylvania before he "crushed" the hellish training on his third try. He served on SEAL Team Five, deployed to Fallujah, Iraq, and taught combatives and prisoner handling to SEAL trainees in San Diego from 2013 until his retirement in 2017.

Sweetman told Fox Digital that "everyone who goes through training is going to get sick."

Tijuana, Mexico, top, and San Diego (Getty Images)

"They're going to get infections, and it's terrible," Sweetman told Fox Digital in an April Zoom interview. "And some might argue that this is Navy SEAL training. You have to go through the toughest conditions to be able to survive and make it. I would say that it's gotten a little bit out of hand." 

The SEAL vet, who lives in the San Diego area, said the issue has gotten worse in recent years as Tijuana's population grows.

Gum and Monroe both said that water issue is a crisis, with Gum identifying it as a national security crisis that could cull well-suited candidates from the SEALs due to acute illnesses as well as sicken active SEALs. 

"This is a huge national crisis," he said. "Like half the SEAL teams are located in San Diego, the other half are in Virginia Beach. So when you've got half the SEAL teams who are getting exposed to this, then it's a major issue." 

Monroe called it the "next Camp Lejeune" crisis, which sickened Marines with contaminated drinking water at the North Carolina Marine Corps base camp for nearly three decades. The crisis has cost the U.S. billions of dollars, including legal costs and settlements to vets and their families. 

"This is going to be, in my opinion, the next Camp Lejeune water problem that cost our government $21 to $25 billion," she said. "That's just in the compensation directly, like the lawsuit portion of it. That doesn't cover all the compensation you have to pay these veterans tax-free for the rest of their lives. I would say that this issue here in San Diego, if you look at it over the time that people have been training here, you're looking at another $21 to $25 billion, plus all of the compensation that's going to come. It would be cheaper for our country to fix this than it would to allow it to continue." 

BUD/S students participate in SEAL training at the Naval Special Warfare Center, Naval Amphibious Base in Coronado, California.  (Gina Ferazzi/Los Angeles Times via Getty Images)

A spokesperson for Naval Special Warfare added in a comment to Fox News Digital that SEALs and candidates' health are a top priority and that officials are monitoring water quality in areas where they train.  

"The Navy takes the health and safety of our personnel very seriously," the spokesperson said. "Water quality at Navy training locations on the beach waterfront is closely monitored in coordination with local authorities. We are fully committed to ensuring warfighters at U.S. Naval Special Warfare Command train in a safe environment." 

Mexican sewage flows into the U.S. (Rob Sweetman)

Ahead of Zeldin's visit, the water flowing from Mexico into the U.S. is as "nasty" as ever, according to Sweetman. 

"What I see here is a tremendous amount of green, nasty water," Sweetman said while pointing at the murky water. "I mean, you can smell it. This is disgusting. As it pours through, it doesn't clear up. There's no clarity to it. It just turns into a foam. And the foam sits on top of the water where it's murky and it just continues to flow towards Imperial Beach and the ocean down here."

Mexico

Donald Trump

Lee Zeldin