Fluid environments can be monitored experimentally through Particle Image Velocimetry (PIV), whereas recent technological developments allow endowing underwater robots with flow-sensing capabilities. This combination opens the way to designing for context-aware robot navigation. However, such innovation demands that flow analysis be carried out from a situated perspective, rather than from the traditional bird's eye view. In this context, we present a PIV post-processing toolbox developed with the intention of bringing the observation point into the flow - to support exploring the sensing picture in a given flow environment, as well as characterizing the flow regime. In order to show how the toolbox can address questions emerging from a situated perspective, we present a case-study in regime-specific feature extraction.