I have used both Treksports and Flows in waterfalls and in-river trails (like the Narrows in Utah) and they both performed really well. Flows have a little bit better traction in wet environments while Treksports have better protection from sharp rocks. But I would use any of them in any water trail.
I don't particularly land on my forefoot when not running, but it does not prevent from wearing Vff's or uncushioned shoes. Unless you are pounding your heels on the ground, you'll be fine. I walked around for many hours and hiked all day in fivefingers with no issues, they are not just for running. However, Lems have a bit of cushion if your feet are particularly tender.
Hey, just got the Alitza, Grey/Rose/Purple, so 21 Vff's, 8 other minimalist pairs.
All Vff models and colors are indicated in my signature, but not the other minimalists': the Stems are light grey, Stems are black, Evo II are the Navy Blue, Off Road Hi in Olive, Boxing Boot in Brown, Lucy Lite Crimson, Konvines are grey animal print and khaki camo.
Went cruising on the Allure of the Seas 3 weeks back. Tried on my new purple Bikila LS while running a 9K and a 5K around the perimeter of the boat on the running track. Also used my Flows under my fins when cavern scuba diving in the Mexican cenotes. My Treksports were worn while hanging from a zip line in Haiti and used to climb a waterfall and visit a cavern in Jamaica. And my Classics on both plane rides and to walk around everywhere. I wanted to use my Treksports for rock climbing on the ship but they did not let me. Needless to say, even though I prefer Europe to southern destinations, it was a fantastic trip.
Do you carry excess weight? There is only so much pressure the skin under the feet and the foot structures can take comfortably without a bit of cushion. I don't have excess weight but I once did. I find that the Lems are good for a little additional cushion without losing the minimalist characteristics.