Not really sure what you’re looking for since the Dead Sea has beaches and water and that is why people are there – to go into the water, meaning they will be wearing some sort of bathing suit. On the separate beaches you might find women in tznius bathing suits, but since it’s already a separate beach, not all women bother to go the extra measure.
ZD – I don’t think it is at all appropriate to suggest going to Jordanian beaches. Don’t you know that a person can be refused entry to some of the Arab countries simply for having an Israeli stamp in their passport. Yes, Jordan and Israel have a peace agreement, but unfortunately not all of their inhabitants are exactly thrilled about that fact.