One of the better summer jobs I had was as a sort of handyman for a rich guy, which mainly meant taking his kids water skiing at their beachfront house on Long Island, near where Perry Como lived. These folks were so wealthy that they had a swimming pool on the beach and German servants who drove a Mercedes. They lived in a Tudor mansion with a satellite mansion out back -- when they imported a tennis pro from Puerto Rico he got his own house. It was idyllic but for one thing: For all their money they couldn't keep the riffraff out of the front yard. The house overlooked Hempstead Harbor: There was a broad lawn, then a seawall, a dock and a yellow-sand beach. The riffraff hung out on the beach. I'd see them in the morning when I cleaned the pool -- scruffy guys in cutoffs walking their poverty-stricken dogs or women collecting wretched shells. I asked the master what we could do and he said, "Nothing." As long as the riffraff stayed below the high-tide line, he said, they were on public property and could parade with impunity. I filed this information, knowing it was only a summer job and I'd soon be trash again myself. If I happened to wash up on some beach, it would be nice knowing exactly whose beach it was, especially since I now knew it was mine. I've been happily washing up on beaches ever since, enjoying the view from wealthy folks' front yards, swimming and fishing or just getting out of the boat long enough to stretch the legs. But lately an alarming trend has developed. Around the sandy shores of Chesapeake Bay and its rivers, signs are popping up with the messages "Private Beach" and "No Trespassing." For a while I thought it was a feeble, legally unjustified attempt by property owners to scare us riffraff off. But it turns out that in this region property owners have much more clear-cut rights to the beach than they do up north, where the tide range is greater and much more property falls in the no-man's land between mean low and mean high tide. These days, faced with growing problems caused by crowds of thoughtless boaters, property owners are exercising their protection against trespassing. "A (Maryland) beach is public domain pretty much only to the point the owner wants to make it public," says Maj. Harvey Cook of the state Natural Resources Department police. Cook says the state owns shoreline between mean low and mean high water, making that part public domain. But in the Bay and rivers here, tides are minimal, so it rarely amounts to more than six feet of beach at dead low tide -- not exactly enough space to put out a blanket and start a bonfire. For all intents and purposes, he says, the state cedes the tidal land to the adjacent property owner. In Virginia, property deeds often specify ownership clear down to mean low water, says Herbert Sadler of the Marine Resources Commission, and if a parcel includes 205 feet or more of waterfront, the owner may apply for rights to an additional adjacent half-acre of underwater bottom, he says. In both states, waterfront property owners appear to be well within their rights posting their beaches against interlopers from the water. Historically they generally have not done so, but now the tide is turning, according to Cook. In Maryland, he says, the number of boats registered has doubled in 20 years to more than 137,000 and continues to grow by 10,000 to 15,000 a year. Many boaters like to get out on people's beaches and "party," an activity that appears to mandate making a racket, breaking things and leaving glass and plastic behind. "It's an increasing problem," says Cook, "due to the inconsiderate actions of b becoming a nasty war. Perhaps the interesting thing about all this is how well the truce between property owners and boaters in the Chesapeake region worked until now. As long as boaters were respectful of beaches and cleaned up after themselves, property owners generally had little objection to occasional visits from roving mariners, says Cook. But these days the visits are becoming more frequent, rowdy and trashy. "There are so many more boaters. They're flocking onto the beaches and leaving their debris around. This is what's causing the property owners to protest." It's a protest, it turns out, with a firm legal foundation.