Is the Megalodon easter egg triggered randomly?

On the bigger Fort de Vaux map (not on TD or Domination), there is a small water puddle which triggers a Megalodon jumping out of it, eating the player. I tried several times but the easter egg didn't trigger.

Does it trigger randomly or is something wrong with my game?

According to this Kotaku article,

an exhaustive search of the map revealed multiple valves hidden in around the map. The trickiest is uncovered by blowing up part of the terrain. Turning the valves creates a small puddle of blood near the capture zone at point C. There is also a additional pipe to be found that you have toss a grenade down to wake the beast. Killing players with melee attacks inside the puddle summons a mighty shark.

So, the valves need to be uncovered and turned, and then in the resulting pool of blood, players must kill each other with melee attacks to get the megalodon to spawn.