SAN DIEGO —The drowning of a sailor who was repeatedly pushed underwater by an instructor during Navy SEAL basic training raises a host of questions, beginning perhaps with this: Why would a highly elite unit made up of some of the toughest, fittest warriors ever to wear a uniform take someone with an enlarged heart and maybe asthma or allergies?

An enlarged heart would not have shown up in the medical exams that sailors are routinely subjected to before they are accepted for SEAL basic training, said Dr. Kirk Parsley, a former SEAL who also served as the Navy doctor for West Coast SEALs until 2013.

Moreover, doctors say it is not uncommon for athletes to develop an enlarged heart from rigorous exercise, and the condition is usually benign, though there is a genetic type of heart enlargement that is hard to distinguish from “athlete’s heart” and can be fatal.

The San Diego County medical examiner called Seaman James Derek Lovelace’s enlarged heart a contributing factor to his drowning death May 6 during a pool exercise in Coronado, California, near San Diego. It was unclear from the autopsy report whether Lovelace’s condition was the more dangerous type.

The medical examiner ruled the death a homicide after finding that the 21-year-old from Crestview, Florida, had been dunked at least twice by an instructor while struggling to tread water in full gear.

The autopsy also discovered Lovelace had an abnormal coronary artery that the medical examiner noted has been associated with sudden cardiac death, especially in athletes.

Lovelace would have undergone a medical exam and physical fitness test before being allowed to take part in SEAL basic training, a six-month program so grueling that 75 percent of candidates drop out by the end of the first month.

It’s unclear from the autopsy report how much Lovelace’s heart abnormalities contributed to his death. But Parsley said the stress of being repeatedly splashed and dunked could have exacerbated his problem.

Dr. Byron Smith, a retired Army doctor and emergency room physician, agreed the heart problems would not have showed up in the medical screenings, but he said there were other red flags: Lovelace had a prior electrocardiogram that found an abnormal heart rate, and he got a prescription more than a year ago for Singulair, which is used to treat asthma and allergies – two conditions the Navy lists as reasons for disqualifying a sailor for SEAL training.

“Nobody should be on medication at that age who goes into the SEALs,” Smith said. “That alone should have disqualified him.”The death raises questions about the safety of the strenuous training, which some argue is necessary to create warriors with missions like the one that took down Osama bin Laden.

No charges have been brought against the unidentified instructor, who has been put on administrative duty while the military investigates.