Liquified H2
"Japan's Kawasaki Heavy Industries debuted on Wednesday the world's first marine carrier that transports liquefied hydrogen, using technology that will vastly expand cargo capacity of the green energy source.
A crowd of 4,000 people gathered at Kawasaki's shipyard in Kobe for the naming and launch ceremony of the Suiso Frontier -- a name adopting the Japanese word for hydrogen. The vessel, measuring 116 meters long, will be fully completed next fall.
Kawasaki will later add tanks that will carry the hydrogen. By liquefying hydrogen at minus 253 degrees Celsius, the cargo can be compressed to one-800th of its gaseous volume.
The carrier will transport to Japan hydrogen produced in Australia from cheap coal, with trial shipments due to begin before March 2021"
Long-distance shipping of hydrogen will not require wildly new, untested tech. We already ship liquified natural gas (LNG) at minus 160 Celcius. Go down little more that gets you H2 storage.