Algorithm is a term to cover a complex maths routine and rules system used in dive computers or software to calculate decompression stops. Algorithms can be less or more safe, depending on level of notoriety the designer seeks. Algorithms have traditionally been designed and validated around strict ( expensive ) testing protocols. However, more recent decompression software titles, especially bubble-model based versions, strangely use a trial and error approach to decompression modeling, typically on the customer base. Historically, bubble-models have evolved from being “far too aggressive” (meaning users get the bends), to “okay” (meaning: that if used ultra conservatively they give tolerable results). Algorithms have been tested on users under the free-ware software scheme for almost a decade. Modern algorithm designers prefer to turn a blind eye to competitors work lest the spotlight falls on them as well. The expressions “Caveat Emptor” or “Downloader Beware” take on a special meaning in technical diving circles.