I suppose it's possible with thigh straps fore and aft and a lot of practice. Mostly you'd just fall off and then hop back on. With a tandem, get on different sides of the SOT. One of you holds it steady while the other hops on. Then that person grabs a paddle and does a paddle brace while the second person hops on. This assumes deep water. It sounds simple, but should be practiced in safe water before having to rely on it for survival.
If you're in a river that's shallow, float it out to a safe place or to a bank and just straddle and sit down.
- Big D
Paddler's Truck Rack