HONOLULU (HawaiiNewsNow) - Full-face snorkeling masks don't have mouthpieces like conventional snorkels. The mask goes over a person's head.
It's supposed to offer easy breathing through your nose and mouth and give a swimmer a panoramic view for a better snorkeling experience.
California visitor Kathie Sylbies bought one for her Hawaii vacation..
"You have a wider view and there wasn't the snorkel mouth piece in the way. It was great! I Ioved it!" she said.
But not everyone is a fan.
Robert Wintner owns Snorkel Bob's. He designs snorkeling gear. He refuses to sell or rent full-face masks after his team field tested the equipment.
"These full-face masks are bad for snorkeling," he said.
Winter said the mask can trap dangerous levels of carbon dioxide as a swimmer exhales, making it difficult to get oxygen.
"Carbon dioxide buildup is known to lead to what we call a gray feeling," he said. "Some people say it makes them sleepy. We know that it can exacerbate panic, which I think is the big culprit in most of these incidents you are seeing now across Hawaii."
Recently on Maui, two visitors drowned while wearing full-face snorkels.
Physician and waterman Dr. Philip Foti is on a state task force studying drowning deaths and equipment associated with ocean accidents..
"I think there is too much focus on this full-face mask as a problem. The fact is that this full-face mask is kind of an extreme example of many of the modifications in or on snorkels," he said.
Foti believes there isn't enough evidence to declare the full-face snorkeling mask more dangerous than other snorkels..
But Wintner said the masks often are poorly designed and don't fit snugly.
"Even a slight movement like squinting can allow water to leak in," he said.
Visitor Daneen Davinna said a full-face snorkel she tried filled up with water.
"I felt safer and more comfortable in a regular snorkel," she said.
Full-face snorkeling masks are sold online and in stores. Some beach activity companies rent them to customers.