Schuler, JulianJulianSchulerGosch, KonstantinKonstantinGoschRenner, Bernd-ChristianBernd-ChristianRenner2026-10-072026-10-072026-0923rd International Conference on Embedded Wireless Systems and Networks, EWSN 2026https://hdl.handle.net/11420/65219Software-Defined Acoustic Modems (SDAMs) are powerful tools for developing, prototyping, evaluating, and comparing novel physical, link, layer and network layer protocols tailored to the specific challenges of acoustic underwater communication. We introduce sd-ahoi, an accessible open source SDAM compatible with GNU Radio and based on the hardware of the open source ahoi modem. We present our design goals and provide a detailed description of the architecture of sd-ahoi. In our demonstration, we transmit text messages between two modems using sd-ahoi while interactively switching between different physical and link layer implementations at runtime.enSoftware-Defined Acoustic ModemTechnology::600: TechnologyConference Presentation10.3217/ydk8-nf41