As far as I can tell from their report (https://gitlab.com/hybrid-drone/paper https://gitlab.com/hybrid-drone/paper), the authors did not consider underwater RF

As far as I can tell from their report (https://gitlab.com/hybrid-drone/paper https://gitlab.com/hybrid-drone/paper), the authors did not consider underwater RF transmissions in their prototype design and simply use standard COTS components typically used for DIY UAVs.