Okay, here it is, the Third Annual Washington Post Conchathon on Sunday Oct. 7: swim 400 meters (a distance half again as long as the Titanic), bike 6.2 miles (about 59 Washington Monuments end-to-end) and run or walk 1.2 miles (the total length of all your excuses for not doing this event already).

But you don't have any excuses this year:

1. You can form a team. Scout out any likely possibilities around you right now. Consider forming a company team. Having a two- or three-person team spreads both the misery and the exhilaration. And need I say one leg of an event is easier than three?

2. Everybody wins. In Conchathons, there aren't any 1-2-3 finishes. Though an official clock will let you check your time, the last person finishing receives the same prize as the first: a Conchathon T-shirt and certificate and the applause of a vast number of admirers. There'll be a cheering throng of at least two.

3. The swimming leg will be in the balmy Smith Center indoor pool at George Washington University. The running and biking segments will be along the pleasant, closed streets around GWU. No more cold water, and for a change the Conchathon is keeping banker's hours: The Conchathon will begin at 9 a.m.

4. You'll be helping the D.C. Special Olympics; $25 of your $35 entry fee is a direct donation to them.

The other $10 goes for your official Tri-Fed triathlete insurance. Hey, think about that: We're talking about making you a triathlete here.

5. The Washington Post and George Washington University's Center for Health Evaluation will even help 100 of you with your medical clearances.

Well, all that alone might be enough incentive to make you get on the exercise wagon for the rest of the summer and autumn. But there even are other perks.

There's a guy named Chris Pollock in St. Thomas, U.S. Virgin Islands, who hates exercise just as much as you do but loves marlin fishing. What some call the god fish. To catch them takes strength and aerobic fitness.

"Okay," Chris said about a year ago when one of the big fish beat him, "I'll swim and run and bike and lift weights and then I'll catch him." A real nice plan with a goal that paid off last week when the 35-year-old Pollock, 20 pounds lighter and in the best shape of his life, tagged and released four giant marlin -- two in less than 30 minutes.

A victory very important to you, since Christopher Pollock is assistant general manager of the Stouffer Grand Beach Resort on St. Thomas.

"I'll tell you what," Chris said after three victory rums poured by me, my tape recorder running discreetly at his side:

"We'll give everyone that finishes the Conchathon a $250 room for $135 a night for any week between the event and Dec. 20, 1990, and just about any week from May 1 to Dec. 20, 1991. And you can have up to four people in the room for that price."

"And I'll give two rooms free for five nights during those days, too. Give 'em away in a drawing when the Conchathon ends," Christopher Pollock, the man tasting his own victory, said grandly.

And that's available for Conchathon participants only (you'll need your certificate to qualify). A Virgin Island Victory incentive for your hard work the rest of this summer.

What to do now:

Decide if you're going to enter as an individual or team. Do two legs, if you want, and don't worry about speed or grace.

If you haven't already written for an entry form, send a self-addressed, stamped envelope (SASE) to Conchathon, Public Relations Department, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071. The deadline for completed entry forms is Sept. 10.

Arrange to have a physical. Sure, that's a hassle, but you probably have been needing one anyway. Most "no-reservation-needed" medical services can do one for you.

Medical screenings at George Washington University's Center for Health Evaluation will be available to up to 100 people at a cost of $50 each. The usual charge is $75 but The Post will pay the difference.

The screening consists of a complete medical history, blood pressure, pulse, cardiac status based on history, a physical examination, and checks of your blood and urine. The tests are going to be run "army style," according to Gary Malakoff, the center's director.

When you send in your SASE, you must state that you'd like to be a part of the GWU evaluation. Include the name and phone number of each person on your team who wants a physical. The Post will contact you with details; remember only the first 100 people who write will qualify for the reduced rate.

Conchathons are great even if you haven't been training: You only compete with yourself; speed doesn't matter. Have a physical, start training now and if you're in generally good health you'll be ready -- particularly if you put together that team.

And in Key West ...

Swim 1 mile, bicycle 10 and run 4. Why stop with October? From Dec. 11-16, when it's likely to be cold and rainy -- or snowy -- in Washington, Key West is at its funky best as the host of its second Conchathon. It'll be five days of fun biking, cruising and power eating (healthy things, of course).

If you want or already have received your application for Key West but haven't returned it, you should call to reserve your spot. Without at least a verbal confirmation, airspace can't be held any longer than Sept. 1. Call 1-800-541-9075. If you need an application, call the same number.