Since Mike responded to the list as well as to Mark, I will also (see
offlist response to Mark below). As an aside, I do have thoughts about how
a pterosaur might be able to break free of the water in a single leap, but
as I mentioned below -- have not quantified it yet. As Mike says, it
certainly possible to break free in a series of initial 'pushoffs'. Due to
the high density of water and the focused loading near the wing finger
pivot, the surface area in contact with the water near the wingfinger pivot
has to be closely controlled -- unlike uniformly varying spanwise flight
loads into the skeletal spar, the water launch loads are almost point loads
(but then, so are the terrestrial launch loads).