Cruise Ships Can’t Sail. But the Behemoth Vessels Are Still a Draw.

While Ms. Wright and other ship sightseers have been part of a tourism wave welcomed by coastal communities, some local residents worry about the ships’ effect on the environment, especially in the seaside town of Weymouth where people have grown concerned about pollution, having noticed a new yellow smog in the atmosphere.

Unlike planes, which are switched off when they are not being used, cruise ships run auxiliary engines when moored out at sea, enabling power for the maintenance procedures and safety precautions in the event of bad weather.

“Most cruise ships operate on heavy fuel oil, which is really thick, toxic, bottom-of-the-barrel fuel,” said Lucy Gilliam, an aviation and shipping campaigner for Transport Environment, a nonprofit group that promotes sustainable transport.

“When anchored they have a base load of energy demand for air filtration systems, keeping the lights on, keeping the auxiliary engines ticking over, being able to do all of that maintenance and cater for the skeleton staff that are on board,” she explained. “It’s not going to be at the same level as if they had a full passenger load, but the chimneys are still going to be pumping out pollutants.”

Local officials in Dorset rejected claims that the cruise ships were causing smog over Weymouth Bay. “The summer weather we have been experiencing is causing temperature inversions — these are responsible for producing smog, trapping the pollutants produced by all vehicles, fires and industrial activities,” a spokeswoman for the Dorset council said in an email.

All the cruise ships anchored across the British coast are required to meet environmental regulations imposed by the International Maritime Organization, which are strictly enforced, according to the British Maritime and Coastguard Agency.