Divers have been searching all week for the 50-year-old woman along a stretch of coastline near Ranchos Palos Verdes.
Vilma Causey has been travelling back and forth between her home in the Valley and Southern California trying to figure out what happened to her daughter.
Investigators say Rebecca's husband told them he last saw her leaving their condo in Del Rey, wearing a wetsuit. Now six days later, Causey still hasn't heard from him, and she says he's acting strangely.
Causey explained, "Very disrespectful, odd, because I would go, 'I want to tell you your daughter is missing,' but I haven't heard from him at all."
Kingsburg mother Vilma Causey recalls one of her daughter's favorite activities, and hopes she'll see her again soon.
Causey described her daughter as, "Very good diver, very strong swimmer, very athletic."
Weiss has been missing since Saturday. Her husband - Alan - told investigators he went looking for her near a spot the two would often snorkel together, after she didn't return home from a day of free-diving. He told them he found her SUV abandoned near a cove, and her dive-bag close to shore.
"They said they found her wallet with a driver's license and credit card in the car, but there's no car keys and telephone."
Since then, divers have been combing the Southern California coastline for clues, while Weiss's family continues to hang posters, pleading with the public for witnesses to come forward.
Nephew David Causey added, "When you go snorkeling people don't notice you but perhaps they saw her leaving."
"If she was there, there's people around," Causey said. "That resort is a lot of people, people are in and out of the beach, in the hotel, they have a restaurant in the open so everyone can look out to the ocean."
While Causey tells Action News she's surprised Alan hasn't helped with the search nor reached out to her since her daughter's disappearance, investigators say he's fully assisted police.
"He's been cooperative without investigators as well as the other members of the family," Lt. Holly Francisco said. "He was the last person to see her so he is being interviewed, but again he was cooperative with investigators."
Investigators aren't sure whether Rebecca met anyone on her way to Ranchos Palos Verdes. They're now taking a look at surveillance video to see whether any cameras captured her movements on Saturday, the day she went missing.