This, sadly. The water would be freezing. Someone died recently doing the ice plunge thing and that’s in a controlled situation. The bank is so steep, climbing out would be very difficult if weighed down, panicked and in shock. Even for a competent swimmer. My Dad’s friend drowned while open water swimming as he had an unknown back issue, he literally jumped in and disappeared.
The speculation, however, is understandable as she has not been found and there is mystery surrounding the circumstances of her disappearance.
Also, the police being almost insistent she’s in the river. Some questions about the handling of the case. Even a less than 1% chance, it should be fully investigated.
The optics aren’t great in the current climate of police mistrust, mismanagement of cases of violence against women etc.