To unlock this achievement you will need to jump over 4 sharks in 10 seconds, 3 of which are in the Lift area sitting in containers, and the 4th needing to be "baited" will appear in the Moon Pool area. When in the Moon Pool area you will notice the giant clear opening in the middle and the three smaller glass panels just outside of it. When you kill zombies on the smaller ones, blood will drain through into the water and attract the shark. You need to get kills on each of the panels (I am unsure if you only need one kill on each or if you need multiple for some of them.) You will have around 15-20 seconds to do so before the blood disperses in the water so you need to be quick. After the shark appears jump over it when it is under the panel closest to the stairs. Proceed running up the stairs and jumping over the shark in the container directly in front of you and then the two sharks that are perpendicular to the stairs. I do not think you can touch the tops of the containers you are jumping over for this to unlock, but I am not certain.
To make this achievement easier I found it best to go for it right from the beginning of a game. After spawning in the Hangar, I was able to get my exo by round 3 and made two attempts for this achievement during round 4. Even a few rounds after round 4, if you buy the AMR9 the zombies will still be very easy to kill and it should still be very doable. On the higher rounds I was having problems with killing the zombies on the panels due to under-powered weapons and then proceeded to get blocked on the stairs by zombies that were still spawning. It certainly is possible on higher rounds, but I would advise against it if you want to save yourself some time.