Having just enough weight to achieve all three states of buoyancy with only minor adjustments in the water is the definition of:

Proper weighting

Explanation:

Proper weighing involves the condition of a scuba diver that is fully geared having a near empty tank and the BCD emptied with a held breadth is expected to float at eye level

The fundamental of adequate or good buoyancy of a scuba diver is to ensure proper weighting when diving, With proper weighting, there is more control for the diver when a safety stop is required. There is less need to carry excess weight that increases drag and gas consumption.  

do you have a formula possibly

305.7

explanation:

density =m/v

density =917/3.00

density = 305.

approximately = 305.7

in four significant figures