The purpose of this paper is to discover and make known the species of aquatic and semiaquatic Coleopters of the sub-order ADEPHAGA which occur in Utah and to give something of their distribution, environment and habits whenever possible. When ever possible the original description or a description from a recent revision has been included for each species. Descriptions given in recent revisions have been regarded as more desirable because they describe the species in comparison with its nearest relatives, while many fo the original descriptions were very incomplete and could not be used to separate many of our present species or even genera, if the types were not known.