Still, he and some other shipping billionaires say they are doing their part. In addition to philanthropic giving, Mr. Martinos said it was important that wealthier Greeks contribute by providing jobs for the country’s increasingly rootless youth, among whom employment is above 50 percent. That is why, despite the slump in his business, he said he had refrained from laying off workers.
“The biggest problem is not feeding young people,” he said. “It is giving them jobs.”
Another rich shipper, who insisted on not being identified because he did not want to draw attention to himself, said that he was providing thousands of free meals to families in and around his ancestral village.
Several shippers said they had also donated to a nascent campaign being organized by the trade group that represents Greek shipowners in Athens — although its president, Theodoros Veniamis, declined to say how much money they hoped to raise.
What the shipping magnates are not doing, though, is paying taxes. Mr. Martinos’s company, for example, bases its fleet of tankers offshore — as do all shipping companies here — although the administrative offices are in Athens.
Greece’s income tax revenue is 7.3 percent of gross domestic product, well below the 11 percent average for euro zone countries, according to Eurostat. Even so, there has been little talk by recent governments or even by Greece’s financial backers about imposing taxes on shippers — a move, it is assumed, that would prompt them to take their business elsewhere.
That is a blow Greece would have trouble absorbing. The shipping industry employs about 200,000 people. And it brought in 13 billion euros in foreign exchange in 2010, making it the country’s top single foreign-exchange earner.
Would shipping’s special tax exclusion change under a left-wing government? It is hard to say. Euclid Tsakalotos, a top economic adviser to Mr. Tsipras, said in an interview last week that the first thing Mr. Tsipras would do was to “tax the people that past governments have been afraid of taxing.”
Mr. Martinos says such an outcome is unlikely, given shipping’s vital role in the economy. Greek shippers are also some of the country’s largest investors, owning large tracts of real estate and interests in tourism, banking and media.
“I don’t think the policy will change,” he said. “Shipping is a net profit for Greece.”
Many shipowners and other wealthy Greeks are said to be taking the long view, arguing that Greeks will come to their senses in the next election and not vote in large numbers for Mr. Tsipras if they become convinced that it means a forced march out of the euro zone.
But privately, they cannot ignore the increasingly grim economic and social environment — which is why some have bolstered their already tight security forces by hiring more bodyguards.
Peter Nomikos, a 33-year-old shipping scion, has started a campaign to raise money from Greek businesses and individuals and then, through a foundation he set up in the United States, use those funds to buy back as many of Greece’s deeply discounted bonds on the open market as possible. The plan would be to retire them to help bring down the country’s staggering debt burden, which is now 350 billion euros — 165 percent of the nation’s G.D.P.
Mr. Nomikos is also building a microbrewery on Santorini, the island of his shipping forefathers. He says that he hopes to create a few jobs in the community and that he plans to contribute 50 percent of the profit to the foundation.
“No single person is rich enough to bail out Greece — not least myself,” said Mr. Nomikos, who through his beer company has already bought 100,000 euros worth of bonds at current rock bottom prices of around 15 euro cents on the euro.