The only point where that formula breaks down is that i weight about 250#, plus gear on top of that, but there is no way i have a 7# swing between fresh and salt water, it seems to be somewhere nearer 4-5# in the same exposure suit! As always its suggested to know your fresh water correct weighting and then add 4-6# for salt, then play with it and correctly work it out when you are in the salt water as well. Just start by adding about 6# from the freshwater in the same suit you intend to use in the saltwater and see if you are too heavy at the end of the dive. Reduce the weighting if you are too heavy at the end of that saltwater dive.
