The assailant kills two female tourists and wounds four others in a popular Red Sea resort town.
Officials said the assailant swam to the beach at the Red Sea resort town of Hurghada before attacking the women.
A man in his 20s was arrested at the scene, police said. The motive for the attack is not yet known.
The two women who died were German, security officials said, while the four others hurt included citizens of Ukraine and the Czech Republic.
Hurghada is one of Egypt's most popular beach resorts, particularly with Ukrainians and other European tourists.
Security has been tightened in tourist resorts around the country as the industry is a major revenue stream for Egypt.
The attack came after five police officers were shot dead in Cairo's twin city of Giza when suspected Islamic militants opened fire on their vehicle early on Friday morning.