Several discoveries, such as Tupi, Bem-Te-Vi, Parati, and Guara, have been announced in Santos Basin off the coast of Brazil, mostly in presalt layers. These layers were well imaged by a salt-flood volume in 2003, but distortions in the base of salt (BOS) and presalt layers were still obvious. Therefore, a constant velocity model is not adequate to capture the velocity variation inside the salt bodies, which include mobile salt and evaporites. A depth migration with a complete salt model is necessary to correctly position the reservoir structures. In this paper, we discuss the challenges in building such a velocity model and share the lessons we learned while working on a data set from the deepwater Santos Basin.