1. The B-2 stealth bomber needed the ability to maintain its speed while diving to avoid anti-air defenses. 

2. The US Navy needed to increase the efficiency of a large unmanned submersible that could function for a long time without needing interference, so they used the highly efficient body design of manta rays to decrease the amount of energy used so that it could function for longer.

3. EU researchers were looking for ways to increase the flight time of drones, so they looked to birds, and their ability to use wind currents and glide to save energy.

4. After looking at shark skin under an electron microscope, scientists noticed that it had tiny scales called dermal denticles that created channels for the water to flow. The grooves lessened water turbulence which made water flow by more easily. This was applied to swimsuits, which were so effective that they have since been banned from competitive swimming.