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It is winter, granted. The beaches are desolate-either windswept and pummeled by angry winter waves or frozen solid in the stillness by the cold.

But in the summer, in gentler days, the beaches are golden, the water azure, and along the 29 miles of lakefront stand familiar sentries: the Chicago Park District lifeguards. For more than 100 years they have guarded millions who have cooled themselves in the waters of the city’s public beaches, lagoons and pools.

And after long, hot, blistering hours on a crowded beach and chill, windy days standing lone sentry along an empty lakefront, they have developed their own jargon:

Waving your orange: A signal by which a lifeguard at the lake alerts colleagues to the need for help in a non-water-related situation, such as a fight, by waving his orange windbreaker over his head. The signal is passed along until it reaches the main beach house and police are called.

Day crampers: Busloads of tots from day camp who must be watched vigilantly because they can’t swim and are accompanied by only a few adults. Their presence cramps the lifeguards’ day when it comes to getting a break while on duty.

Beilfuss shuffle: A stroke used by people who think they swim with style but don’t, and don’t ever put their head in the water, instead turning their face from left to right above the water. The name comes from one of the Park District’s smallest swimming pools, the Beilfuss Pool in the 1700 block of North Springfield Avenue, where long-distance swimming is difficult to do.

Goon boat: The motorized boats used by Park District bosses to check the beaches.

Shake and bake: An initiation for rookie lifeguards at a beach, in which they are thrown in the water and then, while still wet, rolled in the sand, so that they end up looking like a piece of breaded chicken about to be baked.

Moley-o: A lifeguard officer (hence the “o”) who is spying on the troops while they work (hence the “mole”).

IBR: An official-sounding abbreviation for two lifeguards who are dating each other, as in an Inter-Beach Relationship.

Jetty diver: Someone seen walking out on one of the long cement piers on the lake who, because of his actions or appearance, is suspected of being someone who might try to drown himself.

The third oar: An extra oar lifeguards keep in their rowboats, sometimes used for protection against angry or drunken swimmers.

A 3-3: Three blasts from a lifeguard’s whistle to alert other guards that he is going into the water for an emergency.

Face condom: A plastic shield in a sterile pack that a guard wears over his mouth when administering mouth-to-mouth resuscitation.

Acme Thunderer: The lifeguard’s metal whistle, which can be heard for blocks over screams, surf and wind. Made in England by Acme Co., it is worn around the neck and is the only official whistle the lakefront Chicago lifeguard is allowed to carry.

The perch: The wooden tower about 12 feet tall at which lifeguards are stationed. They are not allowed to sit.

The box: The oxygen tank and first-aid kit stored in the beachhouses and at appointed stations along the lake.

Making a jump: When a lifeguard goes into the water to rescue someone.