ABS Safety Standards
The American Bureau of Shipping is the preeminent classification society for civil submarines and submersibles. ABS classed submersibles have a perfect safety record and there has never been a serious injury or fatality to any passenger aboard an ABS classed sub making ABS-classed civil submarines and submersibles the safest form of transportation in the world today. Period.
Other classification societies of other countries also class submersibles but none have the rigorous requirements of ABS and some are simply chosen for their regulatory loopholes. For instance, ABS would never award class to a submersible where opening the hatch in the water would sink the vehicle. In most countries, including the United States, it is illegal to commercially operate a sub not built to classification standards and operated without a valid class certificate. In the U.S. it is at the discretion of the U.S. Coast Guard Captain of the Port as to whether to allow private home-built or non-classed subs to operate without paying passengers in U.S. waters.
Submersibles that are not classed by any classification society cannot be insured and they cannot legally carry passengers for hire.