Family of Navy SEAL trainee who died during pool exercise plans to take legal action The Navy said no one would face criminal charges related to the trainee's death.

 -- The U.S. Navy announced on Monday that no legal action would be taken after Navy SEAL trainee James Derek Lovelace drowned during pool training exercises last May.

The Navy decided that the instructor who worked with 21-year-old Lovelace would not face criminal charges after reviewing the Naval Criminal Investigative Service (NCIS) investigation into the circumstances of his death.

"Our thoughts and prayers remain with the Lovelace family," Cmdr. Liam Hulin, Lovelace's unit commander, said. "No loss of life in training is an acceptable loss."

But Lovelace's family is appalled by the Navy's decision, telling ABC News they plan to take legal action.

"It just makes us sick to our stomach," Lovelace's sister, Lynsi Price, said.

Lovelace was in his first week of elite SEAL training when he drowned during "Combat Swimmer Orientation," an exercise requiring trainees to tread water in full fatigues and boots while wearing a mask filled with water.

At the time of his death, the San Diego medical examiner ruled it a homicide by drowning, saying that while some could consider Lovelace's death an accident, "the actions, and inactions, of the instructors and other individuals involved were excessive and directly contributed to the death."

Price told ABC News that several of Lovelace's fellow shipmates reached out to the family to voice their concern about the events surrounding his death.

"This certain instructor bullied Derek that day and took it too far," she said, adding, "a lot of dunking, just seemed like everything was focused on Derek in the pool that day."

New documents obtained exclusively by ABC News show the Navy's yearlong investigation into Lovelace's case, which includes eyewitness accounts from the day of his death. Fellow trainees said that Lovelace's face turned "purple" as he attempted to stay afloat while an instructor dunked him and put "a lot of pressure on him both verbal and physical."

“One individual was even reportedly considering calling a time-out to stop the exercise,” the report read. “According to Naval records, the decedent was not a strong swimmer.”

Lovelace was pulled from the pool conscious, soon became unresponsive and later died, despite what the medical examiner's report described as “aggressive resuscitative efforts” after he was taken to a hospital. The medical examiner also found that Lovelace had an underlying condition known as cardiomegaly, or an enlarged heart, which could have been a contributing factor.

According to training regulations, dunking and holding a trainee underwater is strictly forbidden, but "adverse conditions," like yelling and splashing, are permitted to create "stress and high intensity."

NCIS cautioned about the medical examiner's use of the word "homicide," saying the term referred to "death at the hands of another," and a homicide is not inherently a crime.

"The only way we can figure this out [is to] file a lawsuit against the government and the instructor and take depositions and see what actually happened," Ryan Andrews, the Lovelace family attorney, said.

Price wants the instructor behind bars.

"Derek deserved more than this," she said. "He deserved honor."

Lovelace's death in May was the third in seven months involving current or former SEAL recruits who had gone through Basic Underwater Demolition/SEAL (BUDS) training.

The deaths led the Navy to institute new procedures for keeping track of trainees who do not make it through the grueling process to become SEALs.

"NSW training has been refined over more than 50 years, informed throughout by lessons learned in combat overseas as well as in training at home. We learn not only from our successes, but also from operational and training failures, mistakes and accidents. While these tragic occasions are infrequent, they greatly impact our small close-knit force and magnify the responsibility we feel to our teammates who have paid the ultimate price," Hennessey said.

ABC News' Luis Martinez contributed to this report.