There's nothing like a refreshing dip in the Mediterranean on a sweltering summer's day. Yet the sea can be treacherous, as it was this past weekend. The surf was up, and so were warning flags atop lifeguard huts. Black flags prohibit any entry into the water; red signify dangerous currents and undertows. Unfortunately, both colors were largely ignored. The upshot: 15 drownings and near-drownings. Five swimmers lost their lives - in Haifa, Atlit, Netanya and Tel Aviv. Many of the injured required hospitalization, with some victims arriving at emergency rooms in critical condition. There were yet more cases of bathers thrashing about helplessly, but pulled out of the water without serious physical harm. In all, it was a catastrophic weekend on our beaches, which is especially sad considering that they are among the country's most enticing recreation and tourist assets. Moreover, the tragedies were avoidable. Most of the drownings and near-drownings (except for two septuagenarians at different locales) occurred at unauthorized beaches where there are no lifeguards. The weekend's tragedies only added to the already existing lawlessness on our beaches: jet-skiers joyriding amid bathers and off-terrain vehicles speeding among sunbathers and children building sand-castles. Just recently, a 28-year-old Swedish tourist was seriously injured when a jeep ran her over on a beach near Haifa. Swimmers who behave with willful disregard for their own safety are being no less lawless, even if they only hurt themselves. The police need to do more spot-checks of popular, though unguarded, beaches. And on legal beaches, lifeguards should perhaps be granted the authority to issue summonses to unruly swimmers who disobey their instructions. It's easy for swimmers to pooh-pooh danger warnings, especially when the water appears calm and lifeguard admonitions seem unreasonably stringent. But lifeguards well know that things aren't always what they seem. It's possible to get into deep trouble even in shallow water. Waves that crash into the sandbars sometimes flow back out with great force, creating potentially deadly rip-currents for even powerful swimmers. Such undertows can remain invisible from the surface, which makes it unsafe to swim where no rescue professionals are stationed. ISRAEL'S authorized beaches number 91 on the Med, 22 on Dead Sea, 25 on the Kinneret and five on the Red Sea. Bathing is forbidden along roughly half of Israel's shoreline. With a growing local population plus the summertime influx of tourists, protected beaches are thus very crowded places. This congestion makes illegal alternatives - clean and unspoiled, and sometimes situated near the authorized beaches - all the more alluring. One solution, as Knesset Internal Affairs and Environment Committee chair MK Ophir Paz-Pines maintains, is to "open up more beaches." And he has urged Interior Minister Meir Sheetrit to do so. Paz-Pines describes legal beaches as "packed sardine cans," and their next-door illegal neighbors as "neglected backyards without rescue services, where swimmers risk their lives." Yet beach expansion is easier said than done. Often there is a reason why the coastline directly adjacent to a legal beach is closed off. In some cases, there is a sheer drop only a short distance away from the water's edge; swimmers, near the shore and with solid ground under them, might not realize they are a step away from extremely deep and dangerous water. Filling in nature's cavernous potholes is a task which local authorities cannot manage, and for which the central government often cannot afford to pay. THE UPKEEP of beaches is an expensive job even for large municipalities. And cities are often unable to outbid swimming pools and country clubs for the services of professional lifeguards. That said, the authorities need to find ways to open more stretches of shoreline to swimming. Whatever can be done without involving inordinately complex engineering projects should be undertaken. Finally, while municipal beaches must remain free to the public, more sections of the coast might be transformed into protected commercial beaches. The existing lack of lifeguard protection in some beach areas is nothing less than a callous disregard for human life. Until that changes, it's down to ordinary citizens not to assume that they are safe from the forces of the tides.