I think that explanation is a crock. The writer seems to have misunderstood something. The exhast of steam powered ships comes out of their exhaust stacks high above the water. Nuclear powered ones have no exhaust, per se. I believe what those trails in the water are showing are the trails of aerated water made by the ships’ screws churning the water, propelling the vessel on its way.
“Steam powered ships”???
Virtually all diesel other than a few gas turbine and nuke.