Wealthy people have so far spent more than £1bn on superyachts in 2021 as they seek to escape Covid lockdowns and travel restrictions, according to a luxury lifestyle publisher.
Boat International said the surge is set to make this year the biggest yet in terms of second-hand sales.
But Oxfam said it was "obscene" that such wealth was not spent on vaccines.
For the cost of those superyachts, the population of Nepal could be fully vaccinated, the charity said.
The trend towards buying superyachts, which started last summer, is the "hottest sales streak on record", Boat International said.
It defines a superyacht as being longer than 24 metres and typically they need a crew.
These smaller superyachts - the bigger ones can be up to 180 metres - usually cost between €1m and €5m (£860,000 to £4.3m) second-hand, and have running costs of about €200,000 per year for crew, mooring fees and fuel, said Boat International editor-in-chief Stewart Campbell.
They can be kitted out with spa pools, sun decks, gyms, or anything else the owners want.
The sales surge was being driven by "a cohort of very wealthy people" who wanted to get away from travel restrictions and covid-related lockdowns by buying a yacht, Mr Campbell said.
While the pandemic had made it more difficult for rich people to jet to the Mediterranean and cruise around, he said, "it's a minor inconvenience in the scheme of things".
More than 50% of superyacht sales are in the US, he said, so people there could cruise in US waters, avoiding travel restrictions.
Many yacht owners "did not want to go near land" due to the pandemic, Mr Campbell added.
He said that it was a misconception that all superyachts were owned by oligarchs, and that the majority of people who owned them had earned their money ethically, and that many gave to charity.
Superyacht owners also contribute to the boat-building and tourism industries in places such as Germany and the Caribbean, he said.
The three biggest yachts sold second-hand this year were Solo, at just over £54m, Elixir, with an asking price of £33.5m, and Lady Sheridan, with an asking price of £24.7m.
But as superyachts go, they were tiddlers. Amazon founder Jeff Bezos's superyacht is estimated to have cost about $500m (£350m).
Oxfam said the £1bn spent on second-hand superyachts in 2021 was enough to fully vaccinate entire countries.
Max Lawson, head of inequality policy at Oxfam International, said: "The £1bn spent in the last year by billionaires on superyachts is more than the cost of fully vaccinating a country like Nepal, where Covid is inflicting a terrible toll.
"It is obscene - a sign of a world that has its priorities badly wrong - that with so much wealth around poor countries cannot get the vaccines they need to protect their people."