The possibility of determining the location of an acoustic source in the presence of gross sediment uncertainties is investigated. Promising results are obtained using focalization, which involves constructing ambiguity surfaces corresponding to randomly selected realizations of the sediment parameters. Due to a parameter hierarchy in which the source location is more important than environmental parameters, it is often possible to reliably determine the source position without determining the correct sediment parameters. The examples involve multiple sediment layers, with sound speeds and range-dependent thicknesses that are unknown. An example that includes both sediment uncertainties and internal waves is also included.