OPA-LOCKA, Fla. (NewsNation) — Thousands of migrants have braved the treacherous trip to the United States along the southern border, but increasingly, they’re coming not by land, but by sea.

U.S. Coast Guard crews in Florida are seeing a rise in the number of migrants from Cuba and Haiti arriving by boat. U.S. Customs and Border Protection has reported a more than 350% increase in migrant landings from 2021 to 2022 in the Miami sector.

In March, NewsNation’s Xavier Walton followed the U.S. Coast Guard during a six-hour migrant surveillance mission. Here’s what he learned from the experience.

U.S. Coast Guard agents have encountered people on rafts or crowded boats taking on water. Even cruise ships have been reported to have stopped to rescue asylum seekers at sea.

“We came across a piece of styrofoam that was maybe 6X8 ft wide and there was three males on board,” said U.S. Coast Guard Lt. Spencer Swanger, who has spent more than 1,000 hours flying over Florida waters. “Just by pure luck, my co-pilot and I not looking out the window, those people wouldn’t have made it. They would’ve died.”

Flying at 1,500 feet, agents can only see so far, so infrared radars and state-of-the-art cameras are used to see miles away.

U.S. Coast Guard Second Class Petty Officer Cherise Bentosino runs the radar. Earlier this year she spotted a group of migrants stranded on an island.

“People just rush out onto the beach; they were weaving their clothes,” she recalled.

After migrants are spotted, crews radio for a Coast Guard Cutter in the area to intercept.

Agents said they’re urging asylum seekers to encourage others and not to make the dangerous journey because it’s not worth risking their lives.

“It really does pull at your heart when you see people who are clearly trying to escape something and all they want for themselves is a better life,” Bentosino said.