Neutral buoyancy is a state in which the sinking force and the buoyant force are suspended.

A boat floating on the surface of the water is in a state where the weight of the boat, which is the sinking force, is balanced by the buoyancy force (the weight of the water if the submerged part of the boat is made of water).

If many divers are on the boat, the weight of the boat will become heavier and the boat will start to sink, but it will stop again when the weight of the boat and the buoyancy (the weight of the water if the submerged part of the boat is made of water) are balanced and the boat becomes neutrally buoyant.

If more divers are added to the boat, the weight of the boat will become heavier and the boat will begin to sink again, but before it becomes neutrally buoyant, water will flood the boat and it will sink.