AdvertisementExperts raised safety concerns about OceanGate years before its Titanic sub vanishedUpdated June 21, 2023Rachel TreismanfacebookEmailOceanGate uses its Titan vessel to take tourists deep below sea level to visit the Titanic shipwreck. It disappeared in the North Atlantic during one such trip on Sunday. (AP)This article was originally published on June 21, 2023.