Rescue teams were sent out to Highway 180 and the Kings River at around 2 p.m. on Saturday where a woman's raft had gotten stuck under a tree.
The woman has been identified as 27-year-old Olga Bayn of Northridge. She was wearing a life preserver, but by the time paramedics arrived, she had been underwater for five minutes.
Witnesses say the group took off from an especially dangerous area.
The public park opened three weeks ago to criticism from people like Tal Cloud, who says the launching point is too dangerous for inexperienced visitors.
"This park should not have been built in this location where there's a chance where people are going to get in the river in intertubes. If you're going to get in the river in this location, you better be in a kayak, with a paddle, and experienced. Anything less than that, there's a problem."
A spokesperson for the group says the park will stay closed until sheriff's deputies finish their investigation and they can ensure the area is safe.
"It's not a good area for floaters to put in, the water is very fast, not easy to navigate when you don't have paddles or a kayak or a raft meant for this are and that's our main concern."
Sheriff's deputies say the woman was wearing a life preserver.
Unfortunately, they say even that doesn't always prepare people for that particular section of the Kings River.