Salt water also makes you more buoyant.
When I took scuba lessons, the final exam was held in a particularly salty estuary. I had to wear several weighted belts to stay down deep enough to perform the tests. In less salty areas, I still have to wear weights (a lot of people do) and when my tank gets to half empty, I end up surfacing like a cork. You can also, uh, FEEL the buoyancy of different body parts.
I think this is one of the reasons there are more male divers. They're just denser and they sink better. I can't imagine anyone Anna's size being able to truly submerge. It must feel strange to be in the ocean.
So basically she is perfectly prepared for surviving her Alaskan cruise if she goes overboard or is swept out to sea?
I wonder how being a deathfat affects being tossed around by heavy waves? Are you more or less likely to break your neck?
I believe standard life vests are designed to keep your head above water. I don't know if they'd do anything for her, or if her unfortunate shape would mean her gunt rises so much that her head could actually be submerged.
In a typical dead man's float (a position you take while alive, not the face-down posture of an actual corpse), your chest is on the surface, as your lungs are full of air, and it keeps your face exposed. Hence why having boobs help not drown. But Anna's gunt and candy juicy are way bigger than her poor lungs or boobs.
I'm being petty though. In calm water I'm sure she'll be fine.
Or if perhaps she crawls into an ice cave and is not able to climb back out again, she has the heat insulation and calories needed to survive until the rescue crews find her.
Might be the best thing to ever happen to her.