There are a number of different technologies to capture CO2 on vessels while they sail. That is not the challenge. The challenge is: where to put the CO2. Ocean going vessels consume on average 200 tons of bunker fuel or diesel or LNG per day. One ton of fuel,( LNG, diesel or bunker) emits 3 tons of CO2 = 600 tons per day. Average journey time is 10 days. Where can you store 6000 tons of CO2 on a vessel?