Answer - nuclear power, which on our submarines has a higher safety history then oil tankers, pipelines, offshore oil rigs or airplanes - all of which contain or use oil, which nuclear powered subs do not. We already have the engineering designs and operational safety regimen’s down pat, and I’m sure some retiring Navy nuclear sub engineers and captains wouldn’t mind new careers that used their professional expertise.
You cannot suggest that...there needs to be wind powered submarines...and solar powered aircraft carriers...!!!
The cost of nuclear maintenance would be far too much for any shipping company.
The reason there are few accidents is because the standards for nuclear plant safety are far above any other machines on earth. To weld a single pipe requires certified welders with security clearance, certified materials and multiple tests/inspections by licensed engineers.
It would also be a target for state sponsored terrorists/pirates so security would need to be at a military level.
Until nuclear is made inherently safe and impossible to be used by terrorists, it will never be profitable in private ships. One bad accident can irradiate an entire continent.