10. Use Iron Lung To Hide Underwater
Of the many perks you can pick up that'll spec everything from melee damage to increased volume of other players' footsteps, one to watch out for is Iron Lung. Primarily used as a way to handle sniper rifles and other zoomables with ease, activating this means your lung capacity underwater is also given a hefty boost.
Perfect for evading fire and swimming around to get the drop on your attacker, using Iron Lung also means you can wait out huge chunks of the round, taking out anyone entering the water, or firing through the surface to catch those on the waterline.
Simply because we don't think of bodies of water as regular cover, they'll never see you coming.