Rivers are far less scary than oceans
Rivers are typically calmer, easier places to stop than the open sea. Large waves, when met at the speeds airplanes travel at, might as well be solid walls. "The stormier it is, the more problematic that landing will be," Bibel said. "The waves can be like hitting hills. They'll break apart the plane and people will fall in and drown."
This was the fate of an Ethiopian Airlines flight that, after being hijacked in 1996, attempted an emergency ocean landing. The plane broke apart on impact; only 50 aboard survived.
Bibel said landing on glaciers can also be safe, so long as nobody hits a mountain. Same with fields, swamps, and other flat spots. That said, he stressed that pilots will ALWAYS try and find an airport, military base, or airstrip to land in the case of emergency. So don't assume you'll be using your seat cushion as a flotation device anytime soon.