There was never a time honoured waterfall model, I quote Winston Royce that wrote the following under the diagram of the standard waterfall process:
the implementation described above is risky and invites failure â¦ The testing phase which occurs at the end of the development cycle is the first event for which timing, storage, input/output transfers, etc., are experienced as distinguished from analyzed â¦ The required design changes are likely to be so disruptive that the software requirements upon which the design is based and which provides the rationale for everything are violated. Either the requirements must be modified, or a substantial change in the design is required. In effect the development process has returned to the origin and one can expect up to a l00-percent overrun in schedule and/or costs.
read craig lahman's overview of incremental and iterative methods to learn the real history.