Cleon
Legend
Ooh yeah, the jaculi! It's in Serpent Kingdoms.
Here are the relevant abilities...
Flying Gore (Ex): A jaculi can hurl itself down on an opponent like an arrow from a point 30 feet or more above. This flying gore attack (+10 melee) deals 1d8+6 points of piercing damage from the jaculi's horns and does not provoke attacks of opportunity.
Spring (Ex): A jaculi can gather its coils and then launch itself in a jump. The jump DCs for both long jumps and high jumps are halved, and no running start is required. Furthermore, when jumping down, the jaculi takes damage as if it had dropped 70 fewer feet than it actually did.
Neither of those seem right. How about this:
Water Leap (Ex): If a water leaper jumps out of water it can fly for 1 round at a speed of X feet (poor maneuverability). It can make a charge attack as part of a water leap. A water leaper can also use its wings as airbrakes, negating falling damage from a fall of any height.