You would be mistaken to think that owning, maintaining and lounging around on a multi-million dollar superyacht is all plain sailing.

Because strict new environmental regulations mean that all large yachts built from next year onward will have to carry huge equipment on board to help curb pollution from toxic gases.

The changes are likely to affect the richest of oligarchs and oil barons, as well as seafaring celebrities including Steven Spielberg, Elle Macpherson and Bono.

Vessels longer than 79ft and weighing more than 500 tonnes that enter US waters after January 1, 2016, will have to be fitted with gear that can convert nitrogen oxides into nitrogen and water

The changes mean all large yachts near North America or the US Caribbean will need to reduce sulfur and nitrogen oxide emissions by nearly 80 per cent.

The laws are expected to also come into force in Europe in the coming years.