NOAA's Index to Marine and Lacustrine Geological Samples has been decommissioned as of May 2025. SESAR is working to maintain this important resource, current database can be viewed here: https://imlgs.geosamples.org/
Additional databases that may be useful include:
Woods Hole Oceanographic Institute Seafloor Samples Laboratory
Lamont-Doherty Core Repository
Scripps Institution of Oceanography
Marine Geological Samples Laboratory at the University of Rhode Island
International Ocean Discovery Program