During the summer of 2022 in the eastern Gulf of Lion (NW Mediterranean), exceptionally warm temperatures were observed down to depths of 30 m, along with massive mortality of benthic species. It has been shown that these deep marine heatwaves are linked to southeasterly wind episodes, which induce deep plunges of surface water overheated by the atmospheric heatwave. These events are rare in summer, but their impact on ecosystems is dramatic and will only increase with climate change.