An ROV can go well beyond 300 metres below sea level.
https://metro.co.uk/2024/08/21/remotely-operated-vehicle-used-bayesian-yacht-search-21462145/?utm_source=dlvr.it&utm_medium=blogger
https://metro.co.uk/2024/08/21/remotely-operated-vehicle-used-bayesian-yacht-search-21462145/?utm_source=dlvr.it&utm_medium=blogger