typical wind/waves in Hawaiian waters channel are 25 kts wind/12 ft seas. When the winds kick up to 30 kts, the seas kick up to 18 feet
I can see how someone in a lifejacket would drown if it did not lift her face adequately above the waves, or if she wore the jacket improperly
Read the article, all that information is in there including the weather conditions. Her life jacket was doing its job. She did not slip out of it and was found floating in it by rescue swimmers.
The crash was not in a channel, just offshore a ways.