I have been following this, and send my most sincere condolences to all who have been impacted by Alison's death...
(Fair warning: this may be graphic)
Someone asked upthread about "signs of foul play" and there not being any obvious indication of foul play.
What can happen to a body once it's been submerged or exposed to the elements is that you have nature going at it...meaning, scavengers may take bites, or fish and/or rocks and/or branches underwater may have snagged the body, and left marks which may have obscured original lethal wounds.
Also, when someone is submerged, they tend to swell and possibly rupture (sorry), and body parts become damaged simply from immersion.
When LE says "no signs of foul play", what they're meaning is nothing obvious; all body parts are accounted for, other sources of wounds are present (as in scavengers), or nothing is obviously wrong (e.g. the head is still attached [again, sorry]).
Further, immersion in water, if for a brief time, may obscure an obvious bleeding spot - there may be stab wounds, but they weren't visible because of the immersion, and blood was "washed" off.
A lot of times, trauma (such as cranial strikes) cannot be seen, even without immersion or scavenger activity. One can have a cracked skull, for example, and have a lot of internal bleeding, but nothing shows outwardly (except for loss of consciousness and/or death).
Last comment, is that bruising/hematomas, even when from a fall-from-heights, requires a beating heart to pump blood to the site of the damaged tissue and to leak from the broken blood vessels. It can be difficult to distinguish pre-, ante-, and post- mortem injuries in the best of times, but in a submerged body it's very hard. The cold water will slow the heart rate and pressure, or consciousness (or lack thereof) will change heart rate and pressure, and so can shock. All of those combined may reduce the body's ability to send blood to the site of damage/injury, and thus no bruising/hematoma will form. And if the body has gone through rigor, and blood has settled, it can be close to impossible to tell outside of an autopsy if there were bruises prior to death.
Autopsy will tell a whole lot more about what's happened. Under a microscope, it can be determined if a cut is a stab wound or a branch snag. It's not always distinguishable, but a lot of times it can be. Same between a scavenger bite and a wound.
Once the autopsy is complete, hopefully there will be an answer to all of this. Until then, we only can wait.
Hope this helps in some small way. Prayers for everyone impacted...
Best-
Herding Cats