It's an annual migration every March, when spring break co-eds flock to sunny beaches and beautiful resorts in tropical areas of the United States, Mexico and the Caribbean islands.

But some don't return home. 

Murders, kidnappings and fatal batches of drugs cut unexpected fun-seekers' lives short.

There's an especially hot spotlight on travel this year after Mexican cartels kidnapped four Americans and killed two of them in the state of Tamaulipas, just south of Texas. 

The U.S. State Department issued a Level 4 travel advisory for six Mexican states in October 2022, including Tamaulipas, and doubled down on Friday when the U.S. Embassy and Consulates in Mexico issued the reminder after reports of a shooting in Tamaulipas. 

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American Cartel Texas

Police officers keep watch at the scene where authorities found the bodies of two of four Americans kidnapped by gunmen, in Matamoros, Mexico on March 7, 2023. (REUTERS/Daniel Becerril)

The five other Mexican states considered a Level 4 threat because of crime and kidnapping are Guerrero, Zacatecas, Sinaloa, Colima and Michoacan.

Here are five fatal spring break cases, along with a travel expert's safety tips. 

Natalee Holloway

Natalee Holloway is one of the most well-known cases of spring break fun in the sun turned tragedy.

Holloway was an 18-year-old from Alabama who vanished on May 30, 2005, the same day she was supposed to fly home from Aruba. 

She and her friends were celebrating their high school graduation and checked in to a Holiday Inn, but she never checked out. 

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Natalee Holloway was last seen in Aruba on May 30, 2005.

Natalee Holloway was last seen in Aruba on May 30, 2005. (AP)

The teen was last seen around 1:30 a.m. on May 30, 2005, after a night of drinking.

She reportedly left a nightclub with Joran van der Sloot and brothers Deepak Kalpoe and Satish Kalpoe, but authorities were never able to nail down what happened next.

** FILE ** This undated family photo originally released by Marcia Twitty shows Natalee Holloway of Mountain Brook, Ala. (AP Photo/courtesy Marcia Twitty) ** NO SALES **

Natalee Holloway, an Alabama native, disappeared in Aruba. (AP Photo)

No one has been charged in connection with her disappearance and her body was never found. Holloway was legally declared dead in January 2012.

Brittanee Drexel

Brittanee Drexel was a 17-year-old from Rochester, New York, who went missing during a 2009 spring break trip to Myrtle Beach, South Carolina.

Drexel was walking between hotels when she was last seen. Her boyfriend, who was in Rochester, became concerned when she stopped answering text messages.

Her disappearance remained a mystery for more than a decade until investigators found her body in May 2022 several miles from where she was last seen.

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A side by side of Raymond Moody and Brittanee Drexel

Raymond Moody was sentenced to life in prison for the 2009 rape and murder of 17-year-old Brittanee Drexel in Myrtle Beach, South Carolina. (Georgetown County Sheriff's Office/Associated Press)

"Today marks the beginning of a new chapter. The search for Brittanee is now a pursuit of Brittanee's justice," Drexel's mother Dawn said after Moody's arrest. "This is truly a mother’s worst nightmare. I am mourning my beautiful daughter Brittanee as I have for the past 13 years."

Brittanee Drexel

Brittanee Drexel, 17, vanished during a spring break weekend in Myrtle Beach on April 25, 2009, and was later found dead. (HelpFindBrittanee.com)

Her killer, Raymond Douglas Moody, was arrested shortly after her body was found, and he pleaded guilty to kidnapping, raping and murdering Drexel.

He was sentenced to life in prison.

Mark Kilroy

Mark Kilroy was a 21-year-old University of Texas student when he went on a spring break trip in March 1989 to the Mexican state of Tamaulipas, the same region where the four American tourists were recently kidnapped. 

Kilroy suffered a similar fate. He was abducted, tortured and murdered as part of a human sacrifice ritual by a Mexican cult. 

His body was found in April 1989 in a mass grave.

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Mark Kilroy was 21 when he was murdered during a spring break trip to Mexico in March 1989.

Mark Kilroy was 21 when he was murdered during a spring break trip to Mexico in March 1989. (Associated Press)

Kilroy's friend, Ryan Fenley, has said in interviews since then that Americans should be careful when traveling for spring break.

"We were planning this big spring break extravaganza. We were going to meet new people, go drinking across the border, flirt and have a good time," Fenley told a writer for Sam Houston State University in 2014, while he was teaching there. 

Mexican Federal police

Patrols of the Mexican Federal police are pictured at the highway between Matamoros and Ciudad Victoria in Tamaulipas State, on December 16, 2015. Mark Kilroy was abducted in Matamoros and killed in 1989. (RONALDO SCHEMIDT/AFP via Getty Images)

"College students today weren’t born at that time, so they don’t know about this case. But, they need to know the severity of it — how big it was."

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Christine Englehardt

Christine Englehardt was a 24-year-old from Pennsylvania who spent spring break in Miami Beach in March 2021 where she was allegedly drugged and raped by two North Carolina men before she died.

She was found dead and "semi-nude" in her hotel room, according to authorities. Investigators said she ingested a "green pill" that was later identified as fentanyl.

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Christine Englehardt died while on spring break in Miami Beach in 2021.

Christine Englehardt died while on spring break in Miami Beach in 2021. (Courtesy of Englehardt family)

The two suspects – Evoire Collier, 21, and Dorian Taylor, 25 – were charged with first-degree murder, among other charges. 

The case is pending. 

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Susan Jacques

Susan Jacques was part of a group of Connecticut high school students who traveled to Fort Lauderdale, Florida, for spring break in April 1986.

The 18-year-old disappeared from her motel room one night. Three days later she was found dead about 35 miles away, floating in a canal west of Delray Beach, according to the South Florida Sun-Sentinel.

Jacques had reportedly told friends she was leaving the motel to take a walk on the beach before she vanished.

Ariel view of Fort Lauderdale Florida coastline

Fort Lauderdale coastline (Hoberman Collection/Universal Images Group via Getty Images)

The Sun-Sentinel reported afterward that Jacques' body was found fully clothed and she was still wearing expensive jewelry, which added to the case's perplexity.

"It probably was a stranger, probably an abduction by guile or by force, into a car," Phil Mundy, a Fort Lauderdale detective on her case, told the newspaper at the time.

Expert's safe travel tips

Kevin Coffey, a travel risk trainer and consultant who was a 35-year veteran of the Los Angeles Police Department where he investigated crimes against travelers and tourists, said it's imperative for travelers to check the Department of State for their destination's crime information and warnings.

He suggested signing up for the Department of State's STEP (Smart Traveler Enrollment Program) service, which warns travelers of significant civil uprisings and violence or natural catastrophes, and downloaded the app "GeoSure," which drills down to the granular level and provides "scores" about nighttime safety, women's safety, health and medical and LGBTQ safety.

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"The majority of leisure travelers can spend 10 to 20 hours looking at their destinations where they want to go and stay and what they want to do, but nothing on safety, security and health mitigation," Coffey told Fox New Digital. "We are trying to get people to change that perspective to prepare for what-if scenarios."

Some "what-if scenarios" he mentioned are lost or stolen wallets or phones or if you get injured or sick.