IT WAS A MURDER! (*enter girly scream)

Everyone either believes that Pipín killed Aubrey or that Aubrey death was an accident or even that she was sabotaged but not by Pipín. I believe none of these were true. Pipín couldn't have killed Aubrey, if he wanted to he would have done so a long time ago. His actions after her death suggest otherwise. "He couldn't eat. Twenty-two pound melted away. He couldn't sleep. He couldn't process the report from Kim McCoy..."

My prediction is that Pipín's old girlfriend, the "blond knockout Jazz singer".

Pipín's girlfriend had a chance to meet Aubrey before the first death.
"Maybe She could go just a little deeper. Ask him a question or two, make
her thesis shine. She watched from across the table as he sat beside his
girlfriend, the blond knockout, the jazz singer. What good fortune that
Pepe Fernandez, the chief of Pipín's safety divers, had gotten an eyeful
of Audrey in her bathing suit and invited her to tag along with the
crew for dinner and drinks."

The moment Aubrey had gotten together there was a death.
"Suddenly she was on his boat a day later,kissing him after a training
dive, when he bolted overboard-the safety diver Whom he’d just met
and hired, Massimo Berttoni, hadn't resurfaced after going down to
retrieve the sled. Suddenly she was staring at death, handling it with
more calm than anyone in his crew. Suddenly she was at the dead man’s
post, with Pipin's life in her hands: She was his new Safety diver at
197 feet."


The second death was Pepe Fernandez.
it was impossible for him to have killed Audrey or the previous diver because he is dead.
There could have been many scenarios in which Audrey could have died. She could have died by the hands of Pascal Bernabé but he was Audrey's dear friend, he couldn't have done it.
To me that leaves Pipín's old girlfriend, (whose name I did not find), she must have been filled with rage. She must have hated Aubrey and Pipín too. She hated Aubrey for taking her man. She hated Pipín for leaving her and choosing Aubrey instead and therefore she is the one who killed Aubrey and the other two safety divers.