The problem is that the red overlap triggers there will fire when -any- Actors enter or leave those volumes. What you want to do instead is test those blue “Other Actor” pins first and only let your players have an effect on those audio components. To do that, drag a wire off of the blue Other Actor pin and type “Cast To” and choose whatever one matches whatever your player class is. This node will have two execution pins, connect the top one to Fade Out node and leave the Cast Failed one hanging empty. Make sure to connect the front pin back to the red OnActorBeginOverlap node.
That way, let’s say you shoot a bullet in the water. Red pin says “yo, somebody entered me” - the next node says “was it a player?” - nope it was a bullet and nothing bad happens. But if you jump in the water itself the red pin says “yikes, here comes another actor” - the next node says “was it a player?” - yes, okay lets play some underwater ambient now.