IN 1977, about a million otherwise normal people are expected to join the 40 million Americans already addicted to that curious form of self-torture known as boating. This so-called sport has become so popular that even if you don't own a boat, chances are you know somebody who does. If you don't, one of these days you will and unless you play it very cool, you may find that you have accepted an invitation to "come aboard" for an afternoon. Or worse, for a weekend.

That's one of the odd things about boating people. Unlike cat burglars or opium smokers they are reluctant to pursue their calling alone. Proof positive that misery loves company.

So beware of the invitation to "come aboard" for these people have a pride that burns with a hard gemlike flame. It is centered in a devotion to the proper use of boating terms, or what one might call the argot of the ocean. It is a devotion not easily dislodged.

If you accept that invitation to go aboard, watch your language. Your host will be miffed if you refer to the deck as "the floor" and he will sulk should you suggest he turn right. On the water nobody turns right. Starboard! (Guests have been known to go to the booby hatch after a weekend of such talk.)

Dress is important, too. Unless you want to be gawked at, don't show up in a yachting cap. Borrow an old baseball cap, the older the better.Only "new" boatsmen wear yachting caps. Dirty tennis shoes will mark you as a real with-it sailor; faded jeans indicate that you are a true man of the sea. Avoid any garment with brass buttons as you would an open manhole.

Okay, you're dressed for it. Now, as you step aboard (which you do only after saying - no matter how silly it sounds - "Request permission to come aboard") you have reached the critical point. Don't greet your host with "Hey, Sam, we brought some beer, can we put it downstairs?"

To begin with, if it's Sam's boat you must address him as "Skipper" or "Cap 'n." And, whether you're toting beer or bourbon, refer to it as grog. The proper salutation, therefore, is "Hi, Skipper. We're toting some grog. Mind if we stow it below?" The skipper won't mind one bit - especially if you're toting a good supply.

Once you cast off (a solemn ritual that involves untying enough lines to secure a tanker) and head down the bay, another tradition as old as the outboard motor must be observed. You must wave.

You wave at everything that passes - water skiers, garbage scows, tugboats, sailboats - anything. It's the code of the sea. The big boats will stare coldly back; the water skiers will ignore you and the helmsman of the garbage scow will curse and shake his fist. But no matter; your skipper will be pleased. And that's what counts.

If you run low on ice, or something like that, don't just wag your hand at a passing craft and yell "Hey, Mac, got any ice?"

This sort of gaucherie embarrasses a skipper. There is a right way and a wrong way. Yours is the wrong way.

The right way is to note the name of the craft you are about to hail. (All boats have names - Mama's Mink; InDebt; Tailgate, Lollypop-and-Mom-things like that.) Having duly noted the name, you pick up the portable bull horn (don't worry, there'll be one aboard) and you speak distinctly into it.

It's ridiculous, but when you're at sea you must say "Ahoy" before you say anything else. Nobody knows why. It's just another of those things about boating. So you say "Ahoy, Tailgate. We're Winnie-La-Pooh out of Lazy Lagoon. Request permission to come alongside."

Chances are Tailgate is out of ice too, but that's not the point. You have observed the code of the waters. You will think all this is nonsense and you will be right, but the nonsense is important to your skipper. It makes it easier for him to swallow those huge monthly payments for his boat.

There's more nonsense about sanitary facilities. These usually consist of an undersized flush toilet crammed in a crevice up forward. It's called the "head" and when you bump yours trying to get in to it you'll understand that one boating term does make sense.

Unless you want to risk being invited aboard a second time, avoid any talk about knots. Any mention of them and your skipper will try to teach you how to tie a bowline; he'll go on for hours impressing you with his lore of such things as a fisherman's bend or a jug sling or the hackamore.

The point is that once a guy gets, hooked on boating he becomes a pusher, trying to hook others. Lord knows why - it doesn't help support his habit.

Maybe it's just that age-old loneliness of the water of the earth. Maybe that's why boatmen wave to each other and why they've invented their own special language.

So, if you want to stay "straight," when you pull into the dock and your skipper orders you to make fast to a bollard with a double hitch, just shrug your shoulders and say "No speak English."

As a matter of fact, that's what you should have said in the first place.