Everyone complaining she wasn't a survivalist... that's exactly why I liked this show. Her stupid mistakes were stupid mistakes that people with no survival skills would actually make.
The deep dive probably was unrealistic, but also... she escaped that plane AND dragged in the drowning guy, and I assumed from that scene the character had a strong swimming background.
Her acting was great. 4 stars because I didn't love the last minute of the show.
Spoiler
I think it would have been more powerful and realistic if she died. I am probably rare in this opinion but... it would have made a powerful and unique ending.