Daily conspiracy

[AFTT47]

At any depth, the sub is floating on the water below it, and sinking through the water above it.  When both sinking and floating yield equal force, it is suspended at depth.

I'm sorry Angrboda but that is not correct. A neutrally buoyant object weighs exactly the same as the water it displaces. There is no cancelling out of up and down buoyant forces - the forces do not exist.

There will almost always be some vertical movement in a horizontally-stationary sub or if dive planes are in a neutral position but that is because of upward or downward momentum and water movement.