According to Egyptian officials, 13 other German tourists and six Egyptian crew members could be rescued from the wreck.
Authorities have begun an investigation into whether the accident was down to the captain's error, or whether “adverse weather conditions” caused the glass to break.
The boat was meant to take the holidaymakers round the island of Magawish, while observing the Red Sea's underwater life.
"We've had high waves and sandstorms for days here. Maybe the boat shouldn't have gone out to sea during such weather," said the operator of a diving school in Hurghada.