The attacks, which took place over a week culminating in a German tourist's death on Sunday days after three Russian holidaymakers and a Ukrainian were mauled, have mystified experts.
A ban on swimming and snorkelling slapped after Sunday's deadly attack in Sharm el-Sheikh has been indefinitely extended, South Sinai Governor Mohammed Shosha said on Sunday.
The ban -- which affects an eight-kilometre (fivee-mile) stretch of beach including popular Naama Bay -- has triggered fears among industry professionals that long-term restrictions could dent the vital tourism industry.
So far, officials say, there have been no cancellations in the dozens of luxury resorts that deck long stretches of white-sand beaches and crystal clear shores which attract up to four million tourists each year.
"We have received no cancellations. There is nothing negative as of yet," said tourism ministry spokeswoman Omayma al-Husseini.
"But if the beaches remain closed, we would be concerned," she added.
"Eighty percent of tourists are leisure tourists, they visit beaches. That is why we would become concerned."
The government is keen to protect the tourism industry, a main source of foreign currency for Egypt, with revenues totalling 10.76 billion dollars last year despite a 2.1 percent decline in receipts in the face of the recession hitting its main European markets.
Tourism accounts for about 11 percent of the country's gross domestic product and provides employment for 10-12 percent of the country workforce.
Around 12.5 million tourists visited the country in 2009, including more than two million from Russia.
Ahram online, the website of the government daily Al-Ahram, on Thursday quoted a Russian tourism official in Moscow as saying Russian tourism to Egypt has dropped 20 percent because of the shark attacks.
"The sooner the Egyptian side settles the problem and provides security at its beaches, the less tourists will refrain from trips to Egypt," Al-Ahram online quoted Nadezhda Nazina, Russian deputy minister of sports and tourism, as saying.
Tourism Minister Zoheir Garana said in February that the government hoped to see arrivals rise to 14 million this year, bringing in revenues of 11.5 billion dollars.
The authorities are taking no chances after Sunday's attack, which occurred just metres offfshore before the eyes of horrified holidaymakers.
They had prematurely opened the beaches after attacks on November 30 and December 1 wounded three Russians snorkellers and a Ukrainian, whom Shosha confirmed was bitten by a shark -- dismissing earlier reports he had injured himself on a coral reef.
Elena Ribac, manager of a Moldovan tourism agency that organises trips to Sharm el-Sheikh, said her company had noticed a drop in reservations.
"I think no one wants to be eaten by a shark. We are not selling as much as before," the attacks, she said.
Foreign and Egyptian experts have met witnesses to the attacks as they try to understand what brought sharks so close to a so-called safe area near the shore.
Experts have suggested that sharks have been lured to the shore by illegal feeding, while others blame their behaviour on changes in the ecosystem.
Shosha said the beaches would reopen either when the sharks have been hunted down or when protections are put in place for swimmers.
"The criteria (for reopening the beaches) consists of two parts. The experts have to tell us how to deal with the shark and capture them. The other thing is to take precautions, such as placing nets in front of beaches," he said.
"We cannot forever ban swimming, we will put nets in front of beaches for whoever wants to swim," he said.
One shark which is believed to have attacked two swimmers last week was caught on Friday but the killer one responsible for the death of the German woman is still at large, officials say.