WPLOT is a utility for the display, exploration, and annotation of acoustic data files. The utility is in Borland's Delphi 2 language, so it can be used from any Delphi or C++ Builder program with little modification to the calling program. WPLOT is geared to examining the raw binary data files produced through the typical use of analog-to-digital conversion cards. WPLOT allows the user to view any section of a data file graphically, handling very large files with the capability to separately save displayed intervals. The vertical scale can be changed to correspond with the extreme values produced in sampling. WPLOT displays the in-line distance of echoes received at the hydrophone given a user-selected sampling rate and an on- screen interval. WPLOT also performs little-endian/big-endian byte swapping, so that data files collected on Macintosh or Sparc systems can be properly displayed. The key feature of WPLOT is the ability to annotate data files, producing a companion description file which consists of 2-tuples, associating a sample offset or sample interval with a token. This annotation is critical for the use of offline processing, such as collecting statistics on bioacoustic events or for use in training supervised-learning artificial neural systems.