The Halifax River, near the popular spring break city of Daytona Beach, Florida, is perfect for boating, fishing and snorkeling. But police say the popular waterway was also the site of a horrible crime.

Crystal Pifer died on the night of August 11, 2015 on that river.

Crystal Pifer could have been the Sunshine State's poster girl: Gorgeous blonde hair, big smile and a personality that shone as brightly as the Florida sun. And growing up near Daytona Beach, Crystal loved the water

"We lived on the water and we had boats and JetSkis," said Fred Campagnuolo, Crystal's father. "She always wanted to swim and go out on the water."

Crystal had one son and worked at her family's towing business. The new man in her life was Thomas Prins, owner of a tree-trimming service.

"Thomas was not the most appealing looking guy but he was very articulate," said Freddy Campagnuolo, Crystal's brother. "He had his own business. He had a house, and I genuinely thought he was a good guy."

Crystal, 28, eventually moved in with 42-year-old Thomas. And her son would often stay over. She was happy -- until one night she wasn't.

"She called and asked us to come pick her up because he was beating on her," said Laurie Campagnuolo, Crystal's mother. After the frantic call, Crystal's dad, mother and younger brother rushed to her aid.

"I saw blood dripping down the side of my sister's face," said Freddy. "Mentally I blacked out, lost control. I tackled him to the ground and started punching him. I said 'If you ever lay your hand on my sister again it's going to be worse.' I thought that was the end of it, I really did."

They all thought that was the end of it. But it wasn't.

Eight months later, on the night of August 11, Thomas planned to take Crystal out on his boat on the Halifax River, a boat he bought from Crystal's ex-husband, a boat he knew had mechanical problems.

"They put the boat down in Port Orange in the Intercoastal Way around 7 p.m." said Joseph Ryan Will, a former assistant Florida state attorney. "They were both drinking."

And almost as soon as they started out, the engine shut down. Reportedly, that's when the arguments began. Eventually Thomas got the boat running and made their way to a nearby restaurant for dinner.

"When they first arrived, patrons of the restaurant describe there had been a heated conversation between the two of them on the boat that lasted for 10 to 15 minutes," said Will. "No one could hear exactly what was being said but body language could tell things were going badly for this young woman."

Thomas and Crystal went inside and argued. Then the mood became a bit friendlier.

"Somewhere during the course of the evening they became overly amorous, their affection was annoying the other customers," said Will. "At some point Mr. Prins tried to get the wait staff to either touch or kiss Crystal."

Management asked them to leave. Back on the boat one of the restaurant patrons took cellphone video of them, sensing things with the couple weren't right. Those would be the last images of Crystal Pifer alive.

Thomas got the boat started, and they pulled away into the darkness. Ten minutes later, again the boat's engine overheats and shuts down, and the couple's fighting picks back up. Crystal jumps off the boat.

"She's distraught, she's upset, he's aggressive, he's yelling from the boat, he's yelling at her," said Joseph Ryan Will.

By chance, a flounder fisherman sees Crystal and tries to help, offering her a ride to shore. But Crystal says no.

"The flounder fisherman tells Mr. Prins 'I'm only going to let her get back on the boat with you if you start being nice and stop yelling at her,'" said Will.

Thomas agrees and Crystal climbs back on board. They push off heading north. But soon the engine overheats yet again. Tempers flare, this time to dangerous levels.

A nearby boater calls 911.

"I'm on a sailboat out off of south Daytona, and a boat just floated by me and a girl jumped out of it and swam over and called my dinghy and said people been beating on her," the caller, James Wagner, told the 911 operator. He tells the operator the woman, Crystal, said she had been beaten on the other boat. As Wagner talked to the operator, Crystal jumped back in the water and swam back to Thomas's boat, telling Wagner she didn't want Thomas to hurt Wagner's daughter, who was in the dinghy.

"So Crystal makes the decision and says to Mr. Wagner, 'He'll hurt your daughter if we go together,' and Crystal dives over the side and swims back to Mr. Prins," said Will.

Crystal and Thomas drift off into the night. Forty-five minutes later, there's a second call to 911. This time it was Thomas Prins.

"Me and my fiancée got into a little argument and she took the keys to my boat and jumped off the boat, and I just want to make sure she's OK," Thomas tells the 911 operator. "I don't see her in the water, I think she swam to shore. She is not that good of a swimmer and I keep on jumping in the water to see if I can find her and I can't find her anywhere. She jumped off the boat, she said 'I hate you' and she jumped in the water and swam off, and I am just praying that she is OK."

Police arrive and tow Thomas in. And with that, he and his boat go home. Early the next morning, two miles away, a local fisherman makes a gruesome discovery: a body floating face down, naked from the waist up. It was Crystal Pifer. She had been beaten and strangled to death.

Port Orange Police Detective Mike Wallace arrives at the scene. There, he's briefed on the argument between Tommy and Crystal the night before, and the 911 calls.

"I immediately observed heavy bruising on her back, some abrasions and contusions and lacerations," said Wallace. "Right then and there I believed foul play was involved."

Armed with the 911 calls from the night before and the positive identification of Crystal Pifer, detectives had a suspect list with only one name on it: Thomas Prins. Prins agreed to go to the station for questioning.

When the interrogation began, Thomas repeated the same story to detectives Wallace and Wenzel: the broken-down boat caused the couple to fight off and on all night, and eventually Crystal jumped overboard.

Detectives took photos of the marks on Thomas's body. Next, detectives wanted to know why Thomas went to the crime scene. And then break the news they believe he already knows, that it was Crystal who was found dead.

Thomas Prins said nothing physical happened between him and Crystal on that boat. Cops believed otherwise.

Detectives showed Thomas photos of Crystal's injuries.

The medical examiner later determined Crystal died from asphyxiation. Police believed Thomas strangled her with her own bikini top.

With not enough evidence for police to hold him, Thomas Prins walked out a free man.

Then, more than two months after Crystal was found murdered, Thomas Prins was arrested and charged after a grand jury indicted him on a charge of first-degree murder. Eight months later the case went to trial. Thomas Prins's defense was the Crystal drowned.

"The medical examiner was satisfied it wasn't a drowning," said former assistant state attorney Joseph Ryan Will. "There was no water in her lungs, there was no water in her stomach."

The prosecution's case included photos of the both Thomas's and Crystal's injuries, and other strong physical evidence.

"We found blood on certain clothes and towels," said Det. Mike Wallace. "We also checked the boat which was parked in his backyard, numerous areas on the boat, they had found blood evidence and Crystal's hair."

And the prosecution had a key witness: Crystal's ex-husband, who had sold Thomas Prins the boat.

"His knowledge of the boat made Thomas Prins and his defense not only unlikely but impossible," said Will. "He was able to explain to the jury the sounds in the background on the 911 call were inconsistent with the story Thomas Prins had given to the police."

Thomas told the 911 operator that Crystal took the keys and jumped off the boat. But Crystal's ex-husband testified you can actually hear Thomas trying to start the boat in the back ground. How does that happen without the keys?

"When you listen to the call you can hear the ignition key turning the background, you can hear the boat motor come on," said Will. "You can hear the engine turn over one revolution, all things that aren't possible if Crystal has the key and is swimming to shore."

The trial lasted three days. Then after just a few hours of deliberations, the jury came back with their verdict: guilty of first-degree murder.

Thomas Prins was sentenced to life without parole.

Many hail Crystal Pifer as a hero, choosing to save Mr. Wagner's daughter that night.

"She went back to her abuser in order to protect someone who was more vulnerable," said Will. "Crystal saved that girl at her own peril."

If you are or someone you know is a victim of domestic violence and need help, contact the National Domestic Violence Hotline at (800) 799-SAFE.