Breakout of objects from soft, clayey seafloors is a common, potentially hazardous and costly task, but there is little information about it beyond results of small-scale laboratory studies extracting decimetre-scale objects from 'model' soils. In this study, a unique dataset is presented, comprising thirty-five immediate breakout events of a seafloor template from very soft clay in 200 m to 2000 m water. The measured breakout forces were compared to operational variables and soil characteristics at the exact location of breakout, which were known because geotechnical soil investigations were performed at each site. Predictions from three existing theories, namely Muga (1968), Rapoport and Young (1983), and Das (1991) were tested. The three theories appear to predict breakout force well, and with comparable accuracy. Predictions from all these methods could be valuable in lifting/extraction risk assessments.

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