Well, here’s the thing….the Army wants their boots on because they are deploying in water to infiltrate on land. I would not enter the water without my fins on my feet. The Army has to have really large foot pocket fins to put them on over their boots too. Then, with boots on, it’s hard to point the foot to have a good propulsion from the fins.
Concerning Force Fins, some USAF Pararescuemen really like them. These PJs are jumping in a different manner than we used in the 1960s and 1970s. Instead of jumping the right door of the HC-130, for instance, they jump the ramp. Also, they now jump either HALO (High Altitude, Low Opening) or HAHO (High Altitude, High Opening). I have not jumped in the modern manner, using square chutes (parawings, actually). Ours at that time were static line jumps, from an altitude of 1250-1500 feet (except for combat jumps, which I never made, at lower altitude), into the prop blast. The advantage of Force Fins is that they are easy to walk in while on the aircraft, and as Bob Evans stated above, provide less surface area for the water entry.
SeaRat