In surveying the hotel grounds, it appears to me in the areas that are unfenced, it would take significant effort to enter the lake via planted vegetation, landscaping, etc.
Where I see the lake would be accessible is the sidewalk or pathway where people walk pets, jog around the lake but that access also requires leaving the hotel grounds. I just don't think that's plausible barefoot in pajamas.
I also understand that underneath the I-95 bridge, there are homeless camps as well as panhandlers on the sidewalk near the lake and the C-14 canal but again don't see any of this applicable around 2 - 4 AM hour.
Lastly, I don't think KG was venturing to the car park as there's been no mention of any car keys missing. In fact, it seems she left everything in the hotel room.
MOO