On relatively flat ground, this isn’t really an issue. If I’m swimming upwards at a 50 degree angle, my forward view angle is tilted upwards in the direction I’m moving, so when I use Look Behind the reversed view is now around 130 degrees.
What I want to see with Look Behind is the opposite angle, like 220 degrees or the opposite direction relative to my forward view angle. That way I will see all the Naga chasing me instead of just an upward view of open water.