Having spent my entire career engineering at sea on a variety of vessels, I can safely say with confidence that the following is what is coming out of the exhaust stacks on diesel engine vessels (approximately 65% of all marine vessels use diesel engines):

Gases:

-Nitrogen Oxides (NOX), formed through the combustion of fuel and air (also regulated quantities permitted under MARPOL reg 13)

-Carbon Monoxides (CO), a byproduct of incomplete combustion (also regulated)

-Carbon Dioxide (CO2), significant component in exhaust after combustion

-Hydrocarbons (HC), unburnt fuel and combustion products (creates smog)

-Sulfur Dioxides (SOX), present in fuel and lubrication oils

Particulate Matter:

-Soot, unburnt carbon

-Ash, inorganic particles from fuel

-Unburnt fuel particles, uncombusted fuel particles including PAHs (polycyclic aromatic hydrocarbons)

-Heavy metals, from fuel and lubrication oil additives (zinc, magnesium, ceroum, iron, manganese, platinum, and copper)

Liquids:

-Water, condensed water droplets in exhaust

-Organic compounds, absorbed onto soot or metal particles

There are so many regulations regarding permitted emissions, sulpher content of fuel, and oil record keeping on board a vessel, which is scrutinised from the 4th engineer taking logs, right up to international Government Organisations, that I find it extremely unlikely that any form of geo-engineering is taking place on board marine vessels as suggested in the original note