<p>Inspired by seawater intake risers (SWIRs), an innovative experimental campaign simultaneously tested three fully submerged vertical cantilevered flexible pipes, each equipped with a ballast attached at its free end, under scenarios of pure towing and towing with aspirating flow. The models were designed to undergo vortex-induced vibrations (VIV) in distinct natural modes, namely the first, second and third modes, with corresponding natural frequencies set to 1&#xa0;Hz. An optical tracking system was employed to record the displacements of reflective markers distributed along the length of each model. The dynamic behavior of the flexible pipes was assessed through displacement time series, spatial amplitude spectra, and modal decomposition, including amplitude time series and modal spectral content. Among the new aspects brought by the paper, we highlight the experimental evidence of internal structural resonance effect, characterized by energy transfer from a dominant vibration mode in its upper branch of response to other modes. Additionally, the tests conducted under combined conditions of towing and aspirating flow revealed that the influence of the aspirating flow on VIV is minimal, regardless of whether the internal flow velocity is below or above the respective critical value. This confirms the dominance of the VIV phenomenon and that the effect of the aspirating flow may be interpreted as a weak damping. The results herein presented provide new benchmark data for the validation of mathematical models describing the behavior of cantilevered flexible pipes under the effects of pure VIV, as well as to the simultaneous action of VIV and aspirating flow.</p>