Plotting Ways to Keep Your Cool at the Beach : A portable cooler/ warmer helps summer food stay fit, while a dog’s life may now be preserved.

For most travelers, summer means a substantial amount of time spent at lakes and beaches where two elements prevail: heat and water. While these are quintessential qualities of the season, they pose problems for food that’s best kept cool, gear that’s best kept dry, and even the family pup--whose exuberance in the surf may be dangerous to his health. The following products are apropos of the hot, wet season. Prices do not include shipping and handling.

Insulated coolers and ice chests may suffice for short spells and for food that is safe at middling temperatures, but for lengthy car trips, you may want to consider a portable electric cooler/warmer that plugs into a standard car cigarette lighter and keeps its cool (or heat) over the long haul.

Employing a matchbook-size thermo-electric module in lieu of the bulky refrigeration coil, compressor and motor used in conventional refrigerators, the compact fridge will cool to 40 degrees Fahrenheit below the surrounding temperature. A flick of a switch converts the unit into a food warmer that keeps food at about 120 degrees.

Called a Koolatron, the unit comes in two sizes. The smaller, 13 inches long by 9 inches wide by 11 inches high, weighs 6 pounds and has a capacity of 9 quarts (about nine 12-ounce cans of soda). The large size, which measures 21 inches by 16 inches by 16 inches, weighs 17 pounds and holds 34 quarts (the equivalent of 40 12-ounce cans of soda). Both units have low power draw (2.5 amps, about the same amount as a tail light), so neither should pose a problem of battery drain.

I tried out each unit on separate weekend getaways. Both performed as promised. As indicated in the instruction manual, food placed closer to the cooling (or heating) element stayed cooler (or hotter). Though it’s much bulkier, I preferred the larger unit, since it holds about quadruple the food of the smaller model, providing plenty of space for large bottles and casserole containers, which justifies its weight, size and cost. The smaller unit has such a limited capacity that it really doesn’t seem worth the bother (or price). The manufacture wisely made the power cord 10 feet long, allowing the cooler to be kept in a car’s back seat (the large unit takes up about the space of one person; the smaller one could be stored on most car floors).

One thing to keep in mind: With the capacity to lower temperature 40 degrees, the unit will cool fine in an air-conditioned car. In a hot spot, however, say 90 degrees, food will only chill to about 50 degrees Fahrenheit--not safe for perishables for a substantial length of time. Also, if your car is the kind where the cigarette lighter does not function when the ignition is off, the cooler will not function then either. An optional AC adapter is available for both models, allowing the unit to be plugged into any three-prong, 110/120-volt outlet--a useful feature poolside, at electrically wired campsites, in motel rooms, or as an auxiliary fridge at home.

Koolatron Portable Cooler/Warmer, $150 large size, $110 small size, $55 for optional AC adapter, available from Frontgate, an Ohio mail order company; (800) 626-6488.

On a simpler note, here’s an attractive solution to the problem of keeping valuables such as passports, cash and keys dry while engaging in water sports or simply romping in wet places. The Dry Pack 210 is worn around the waist and has an adjustable belt with a plastic clasp. Items to be kept dry are stored inside a spacious waterproof pouch, the flap of which is folded over tightly several times, then buckled to keep the closure tight. Water-safe items can be stored in the outside mesh pocket, which has a drawstring to secure the contents.

I found this product useful whether kayaking or strolling the beach. Note, however, that while the dry pack is water-resistant, it is not waterproof. The pouch did fine during brief dunkings and endless splashing, but ultimately leaked during prolonged submersion--as the manufacturer warns in its advertising literature.

The Drypack 210 (item No. 7002) is $22 from TravelSmith, a San Rafael, Calif., mail-order company; (800) 950-1600.

Videocassettes are particularly vulnerable to heat, sand and water. Sony has addressed that problem with its Sports Metal HG, an 8-millimeter, 120-minute videotape that comes in a transparent hard rubber case. The videocassette, a standard high-grade metal tape, is not water-resistant, but when stored in the heat-resistant, airtight rubber case, it is protected from bumps, water and high temperatures.

As someone with a tendency to throw my videotapes carelessly about--leaving them on hot dashboards and in bags where they’re susceptible to dirt and worse--I’ve found these units handy. Of course, now I have to remember to put the videocassette back in the case, but that’s another matter.

Sony Sports Metal HG is $12 at camera stores and other video suppliers.

No need to get a wet and/or sandy derriere at the beach. Lands’ End’s pop-up beach chair, which has lightweight aluminum legs, provides sturdy seating, then folds back up for easy carrying.

I bought a pop-up chair for use at picnics and outdoor music concerts. While it was plenty comfortable for me, I don’t recommend it for people with serious back problems. Also, the polyester material can get hot and sticky, a problem easily solved by covering the seat with a towel.

Pop-up Beach Chair (1985-2115) is $40 from Lands’ End; (800) 356-4444.

But enough about people. Pets are beach-goers too, and the Texas Recreation Corp. of Wichita Falls, Tex., thinks the canine set could use a little extra buoyancy when it takes to the water. The company’s soft vinyl foam dog life preserver, available in six sizes and two colors (pink or blue), is designed to keep the animal from tiring and sinking when splashing in the deep. The life preserver has two holes for Fido’s forelegs, and two straps that buckle at the dog’s back.

I used a friend’s terrier as a guinea-pup, with mixed results. On land, the dog appeared annoyed by the contraption, rolling around and biting at it. In the water, however, the life preserver seemed unobtrusive--though you’d really have to ask the dog to find out if it made swimming easier. Because the vest is plastic, it can get quite warm and binding, so it’s a good idea to remove it when the dog isn’t water-bound. But the vest seems to make a good safety precaution for boat outings.

To determine the size, measure the dog’s chest behind the forelegs. Sizes are S (11-13 inches), M (15-17 inches), L (19-21 inches), XL (23-25 inches), XXL (27-29 inches) and XXXL (30-34 inches). Dog Life Preserver in pink or blue (B38-0562) is $25 in S, M, L and XL sizes, and $30 in XXL and XXXL from Pedigrees, a New York pet products catalogue store; (716) 637-1434.