what is the diffrernce when considering the buoyancy effect and when not consider it sihat

I am not very clear here but generally if you are talking abt bodt weight in water subjected to buoyancy, as far as the forces are concern it should not take any effect. That is because you are not taking weight into account. However, if you use MDM through UDF of 6DOF, then it may be well worth it to consider submerged weight due to buoyancy. Well thats the answer if I get your question right. Sham.