She failed to surface.
"We're all worried about her," says her brother Robert Lashlee.
He says Tamara has scuba dived before and knows what she is doing.
"But she isn't as experienced as her brothers," says Lashlee.
Her brothers remain at the scene as Mexican search and rescue patrols continue to look for her.
"All we can do is stay busy," says Tamara's mother Emma. "That's what we've been doing all day."
CNN is also reporting that seven private ships from tourism and scuba diving services have joined the effort as well.
A local diving expert says the waters off the coast of Cozumel can be tricky.
"There's a current that runs up the side of the island year around, very consistent," says Dave Mohowski of Dive Utah. "Rather than fight against the current, divers are going to hit the water usually as a group, drift as a group and then surfae as a group. Rather than fight against it you go with the flow.
He says those currents can lead to problems especially if you get seperated from the group.
"If you get seperated from the group the current can take you,"
He says divers normally are equipped with gear that includes a floating device.
"If she deployed it then it's possible she could be floating and drifting out there," Lashlee says.
And that's what the Lashlee's are hoping for.
"We've heard they can stay afloat for days and days," says Emma Lashlee. "We hope she is still alive."