RESIDENTS of Marina Cove are threatening to set up their own team of guards to protect the posh enclave from villains and riff-raff. The move has been prompted by a series of crimes at the swanky estate in Sai Kung, including burglary, car thefts and kidnapping. Residents' demands: 1. Soldiers to be hired to guard the place - ''consider hiring Gurkhas''. 2. An independent ID card to be issued to all Marina Cove residents. 3. High-walled entrance gates to be built. 4. Outdoor closed-circuit television cameras to be installed around the estate, to watch people's movements (Singapore government officials, eat your hearts out). This is not a joke. ''If your company is not going to do the job, we are going to form our own security company in place, or seek outside expert security services,'' the residents have written to Henderson tycoon Lee Shau-kee, builder of the luxury residential complex. One is reminded of the old Ealing movie, Passport to Pimlico. Copies of the battle plan have been sent anonymously to all residents, the police commissioner and Lai See. This is all very well, but we wish the residents had had the courage to sign it. What is the company supposed to do? Reply in skywriting? Anyway, we foresee the following headlines over the next six months: Marina Cove Demands Free Elections. Marina Cove Gazettes Independence Bill. 'Man of Guilt Patten Personally to Blame for Marina Cove Talks Breakdown,' Claims Lu Ping. Ivy's got it taped RECEIVED a letter from the Hongkong Association of Secretaries telling us about a secretaries exhibition at Cityplaza, Taikoo Shing on Thursday. ''Should you have any questions regarding the above, please contact Ms Ivy Chu at 573 5502 (recording machine),'' it says. Funny name for a recording machine. Norm disarmed HONGKONG publisher Thomas Bate has just returned from a business trip to Vietnam. A British colleague on his way to meet him stepped into a lift in the Rex hotel. Inside, he met a slightly chubby American man in his mid 50s. The Brit stared at the American. ''You know,'' he said, ''You look familiar to me . . . but I can't place you. Didn't you used to work for the American Government?'' The American replied: ''Yes, but I've quit,'' with a laugh. It's a good thing he was in a good mood. It doesn't do to get on the wrong side of Stormin' Norman Schwarzkopf, because that's who he was. Norm probably keeps a couple of Patriot missiles on his person. Doctor's orders THIS story came our way from the Ladies' Recreation Club yesterday. A young male member, so to speak, has recently been strutting around proud of his new membership. Then he read his bill and was shocked to find that he has been overcharged. Someone else's bills had been added to his, he reckoned. Annoyed, he rang up the management to complain. ''You keep charging me for someone else's chits,'' he fumed. ''Who?'' they asked. ''Doctor Ajit,'' he said. The managment pleaded not guilty. After much analysis, two things were eventually discovered. 1. There is no Dr Adjit at the club. 2. The management shorthand for writing ''Debit adjustment'' on bills is ''DR ADJT''. Off Mark DESMAN Advertising Agency of Willy Commercial Building in Sheung Wan is writing to business people in Hongkong, boasting that the firm offers ''Reuabiuty''. Recipient Mark Majzner of Saitek replies that he will definitely use Desman the next time he wants reuabiuty. Can't say fairer than that. Check-mate READER Barry Mortimer was reading a Casio manual which includes a list of spell-checking devices, including the ES-610, described as ''Spelling Checker with Financial and Legel Terms''. If Casio spell-checking programs are so brilliant, why don't they use them themselves? Tap the market UH-OH. The makers of last year's hit toy Super Soaker, the pump-action water gun has come out with new, even more powerful water weapons, according to Advertising Age magazine. Watson's has been selling pocket versions of the water guns for a mere $15. Other toy-makers are also looking to hose down the public, including Cap Toys, whose Robo Blaster battery-powered water gun has a range of up to 80 feet. Now we would not want to put ideas in anyone's mind, but this would go from the back row of the public gallery right across the Legislative Council chamber. Yes. No offer COMPAQ, the computer firm, is sending out information about cut-price systems. ''Offer expires while stock lasts,'' it says.