During subsea lifting/lowering operations, offshore operators typically utilize published regulations or recommended practice (e.g. Ref 1 & 2) for calculating key parameters such as maximum and minimum crane wire tension during deployment through the splash zone and through the water column. First hand observations by the authors has revealed shortcomings of accepted practice in key areas such as: 1. Over-prediction of wire tension and snap loads, leading to lesser weight being lifted 2. Under-prediction of underwater heave motion of module while being lowered These issues are discussed in light of the fact that added mass of the module changes with submergence. Model tests and numerical simulations using DNV's software SESAM are used to evaluate the added mass of cylindrical and rectangular modules and to gain an understanding of heave motions experienced by the modules in moderate wave conditions. Sample calculations are used to show areas where existing regulations are inadequate.