The flood waters were raging through South Lake Houston Parkway. What was typically a quiet suburban street had become a treacherous river, thanks to Harvey’s rains. Alex and Glen Mayo pulled up in their boat. A short distance away, three men—members of the Cajun Navy whose boat had capsized during their own rescue efforts—clung to a tree, now in danger themselves. Without looking back, Alex leapt straight into the water.

Both father and son are members of the Houston Police Department’s Dive Team, trained for exactly this type of high-risk situation. But Glen was afraid for Alex not as a colleague, but as a father. His eyes betrayed terror as, days later, he recalled the moment. “My son went into the water, into the current,” he said, his voice cracking. “As a parent, that was one of the toughest things for me.”

Soon, everyone was safe onboard the boat, thanks to some careful maneuvering by Glen, some rope, help from a few other officers, and Alex’s bravery getting to the men in the first place. The Mayos took a moment to snap a selfie to send to worried loved ones. “Don’t worry,” texted Glen. “We’re okay.”

Alex and his father have been diving together since he was a boy. “I knew this is what I was going to do since I was 12,” said Alex. Glen himself has been hooked—and served on the HPD Dive Team—for decades. After a seven-year stint in the Army, Alex joined his father in 2014.

The Mayos take rotating on-call shifts with the Dive Team. The rest of the time, Alex serves with the South Gessner Tactical Unit, while Glen is a K9 officer at the airport. Most dive operations, they say, are relatively routine: drownings, evidence retrieval, car accidents that end up in the bayou or Houston Ship Channel. But Glen has seen his share of floods, including 2001’s Tropical Storm Allison. And Harvey, he explained, was a completely different animal.

“In Allison, I was in a confined area,” he said. “But in Harvey, we’ve been all over the city and outlying parts of the county.” The storm presented unique challenges, including the need to maneuver through city streets not knowing what lurked beneath the water, from submerged cars to street signs to fire hydrants.

Often, evacuees were panicked, their pets frightened. “One lady had a small kitten wrapped in a blanket,” Glen recalled. “I said, ‘Give it to me.’ I’m holding this kitten with one arm and trying to fight swift currents with the other.”

Both worked for more than 35 hours straight without sleep and little food. In the end, they rescued well over 3,000 people, they estimate, between the 16 officers assigned to the dive team. One of the scariest scenes was an apartment complex on Woodforest Drive in northeast Houston. Greens Bayou had swollen, surrounding the three-story building with what was essentially a fast-moving river.

“The currents were just ripping,” said Glen. “There were people on the roof screaming, water in the building like you wouldn’t believe.” With help from the military, other officers from around the country, and quite a few civilians, they managed to get every single person out of the complex safely.

And despite having to save a few of the volunteer helpers, Glen said he’s incredibly thankful for everyone who assisted in rescue efforts. “There’s no way we could have pulled everyone off the roofs by ourselves,” Glen said. “Thank God for the Cajun Navy.”

Father and son said they won’t forget experiencing, firsthand, the outpouring of help on display on TV and through social media. Alex recalled people running up to him during the storm. “They saw the police patches and said, ‘Where do you need me? What can I do?’ It was really touching.”