IF IT'S breakfast it must be morning.

"It's the only way you can tell," explained Victor Contreras, one of 118 crew members of USS Pogy, a nuclear submarine he calls home for more than 200 days a year. Since he and his mates are likely to see port only once a month, and in the meantime live underwater on an 18-hour schedule, morning is only morning because there are eggs and hash browns instead of hamburgers and french fries.

The Pogy, commissioned in 1971, is one of the U.S. Navy's 89 fast-attack nuclear submarines; and, like all of them, the only thing that requires it to surface is the need for more food for its crew. Everything else is self-generated, including oxygen and up to 8,000 gallons of fresh water a day.

But at the start of each deployment, the roughly 300-foot-long and 38-foot-wide dolphin-shaped vessel must be crammed with enough food for 1 1/2 to three months at sea--480 pounds of food per day costing $4.06 per man, or 39 cents more than on a surface ship. Unlike the German submarine-turned-film-star Das Boot, where one of the two johns was stacked with food, the Pogy's seven johns are left free, but as Commanding Officer Archie Clemins warns visitors, "We end up walking on food." The passageways are lined with No. 10 cans, one case high, and topped with cardboard or plywood when the ship is fully packed. The first days out, the crew members hunch down the corridors.

"You more or less eat your way down," explained supply officer Bob Whitaker. The first place you try to eat your way out of is the crew's mess; the last is the bunking areas.

It takes forethought to pack the ship so that a variety of foods will be unearthed at each stratum. "If you get to a certain layer in the freezer and all you have is okra, it is a problem," said Whitaker. And the officers of the Pogy groaned in unison at remembrance of okra problems past.

Balancing the purchases between fresh, frozen and dried foods is even more complicated. The 2,000 cubic feet of freezer space can be converted to refrigerator space, and vice versa, so decisions must be made on fresh vs. frozen--all the fish is frozen--as well as bulky versus "ration-dense" (dehydrated) foods. The fresher the better, of course, but fresh foods are bulky as well as perishable. Then canned foods are preferred to boxed, since cardboard is susceptible to roaches. And to complicate the storage restrictions, thousands of trash disposal weights must be carried so that garbage doesn't float to the top of the sea. The space program has made major contributions toward developing dehydrated "ration-dense" foods, which require very little space--a 15 1/2-ounce can of green beans provides 50 servings--and keep indefinitely. But those foods are expensive.

Another major improvement in underwater dining has come from dipping fresh eggs in wax so that they can be kept for 60 days without spoiling. Extra eggs are stored in the emergency escape hatch.

The only fresh vegetables brought aboard are salad fixings; there simply isn't room for other fresh vegetables. But fresh coffee is a luxury still indulged; most ships have switched to freeze-dried, but the Pogy stands fast, even though coffee is one of the bulkiest items, like flour and sugar. Frying oil is also bulky, as is cola syrup. On a long deployment, the soda machine is the first thing to go, and the crew is limited to powdered juices and reconstituted iced tea. The vitamin C-fortified juice solves the scurvy problem, that traditional scourge of navies.

Milk can be kept fresh only five days (30 to 36 gallons being consumed each day), then the crew, with much regret, makes do with dried milk. Lettuce keeps up to a month, and if there is room in the refrigerator the tomatoes do, too. Then the kitchen switches to three-bean salad and dehydrated cabbage.

After a month of squeezing past each other and hunkering into bunks not much bigger than your shirt drawer at home, little treats become more important. A crewman may hit that cola machine 15 times a day, particularly on the quiet night watch. And videotaped films are accompanied by the sound of four popcorn poppers running constantly. "We use about five cans of popcorn a night. It depends on how good the movie is," said Clemins. A sudden fad can wreak havoc on supplies; once when a commanding officer was on a Tang kick, the whole crew caught onto it and quickly depleted the supply. Peanut butter is always a big hit (Climens eats peanut butter and tomato sandwiches), and the officers shudder when reminded of the time the Pogy ran out of its favorite brand of chunky peanut butter and was reduced to the Navy's brand. The next run, each man brought his own peanut butter on board. The Pogy stocks no candy, but the cooks do whip up trail mix for snacking.

Gaining weight is a perennial problem, particularly since the only exercise equipment is a single treadmill (the Pogy is trying to acquire a stationary bicycle). After a while, the crew naturally cuts down to one or two meals a day--and sleeps only four hours a night. And they stop talking about food--unless it goes wrong. In any crisis the crew becomes either hungry or tired--in either case, wrecking the kitchen's meal planning by quickly depleting dinner or leaving it uneaten. Talk about food picks up when the Pogy nears port, where the ship will stock up on fresh vegetables and fruits (which are consumed nearly before they are brought on board) and the crew stocks up on "gedunk," or the kind of junk food they buy in vending machines, where dropping in the money sounds like gee-dunk.

Seven cooks prepare four meals a day in a kitchen not much bigger than you'd expect in a suburban singles condominium. All the bread--14 loaves a day--and pastries--an average of eight pies, cinnamon rolls and the like--are baked on board (Clemin's worst memory is of being on a ship that ran out of yeast). Everything is strapped, tied or latched down. The deep fryer is very, very deep. And no cooking with open flames is allowed. No crepes suzettes. Besides, no booze to flame them is permitted on board, no cooking wine or even any vanilla flavoring containing alcohol. Canadian ships have full bars, while U.S. ships have special no-alcohol rum flavoring. Two ovens, one grill and a large Hobart mixer turn out the food, which the cooks prepare by regulation Navy recipes, designed to serve 100.

The crew's messroom is the social hub of the ship, its five vinyl-covered booths being the enlisted men's only lounging place on board. It thus serves as dining room, card room, movie theater, front porch. The food in the enlisted men's mess is served cafeteria style, while the officers' mess, around the corner, is served and set more formally, with tablecloths and napkin rings, china and silverplate, stemmed glasses rather than mugs for cold beverages. Fourteen officers gather at this table, which, though it hasn't yet been tried, is also the ship's operating table.

While mess management specialist John Martinez, the Pogy's leading cook, became a Navy cook in order to please his commanding officer, several of the others had worked in restaurants before they joined the Navy. David Stewart had cooked in steakhouses back home in Missouri; Roger Rossbach had studied cooking in high school, then cooked in restaurants across the country, joining the Navy because Hawaii was the only state he hadn't seen, and "It was the fastest way to get there." A legend in the kitchen is Bruce MacIntosh, whose creativity extended to tinting the bread with green stripes for St. Patrick's Day and the hamburger buns like rainbows.

In general, though, they faithfully follow the Navy's recipes; 36 cans of cream of mushroom soup are on board to help them do so. Creativity is limited to baking and mid-rats (midnight rations); though drab routine is livened by garnishing dishes with oranges and maraschino cherries.

Menus are set before the ship leaves shore, with the commanding officer's approval. The chicken cacciatore recipe disappeared from the repertoire (the captain is said to have hated it). The lasagna recipe card, on the other hand, is well stained, obviously a favorite. Tacos are considered a treat, though since they smash easily, "If you get a whole piece you were probably first," joked Clemins. And the few times steak or lobster tails are served, everyone gets up for the meal, even those asleep--otherwise unheard of.

In planning meals, the staff follows the advice of a Navy nutritionist and food service team, but hasn't cut down the frequency of hamburgers sufficiently to satisfy those advisers. Portions are figured at 1,400 calories per man per day, but the crew is said to actually eat twice that. According to some crew members, they eat better on the Pogy than on shore--more balanced meals, less junk. They eat foods they would never eat at home, perhaps beef stew or asparagus. The first food they head for in port is a hamburger and a beer; and they find that after being dry underwater for a month, three beers can knock them out.

What crew members say they miss most--besides privacy and walking in a straight line--is milk. And though they prefer, above all other foods, the American standbys--hamburgers, hot dogs, pizza--these are, after all, Navy men. Thus, as cook Roger Rossbach put it, "They really enjoy a good gravy."

And here is theirs: NAVY GRAVY (100 servings) 3 cups meat drippings and clear fat or shortening 1 1/2 quarts general-purpose wheat flour, sifted 2 gallons hot stock 4 2/3 tablespoons salt 1 tablespoon black pepper

Sprinkle flour evenly over drippings and fat in bottom of pan. Scrape up and incorporate brown particles remaining in pan. Cook over low heat on top of range or in 375-degree oven for 30 minutes until flour is a rich brown color. Stir frequently to avoid over-browning. Add this browned roux to stock, stirring constantly. Bring to a boil, reduce heat, simmer 10 minutes or until thickened, stirring constantly. Add salt and pepper. LASAGNA (100 servings) 30 eggs, slightly beaten 5 1/2 quarts cottage cheese 1 quart, plus 1 1/2 cups grated parmesan cheese 6 tablespoons dehydrated parsley 6 pounds lasagna noodles 2 quarts, your favorite meat sauce recipe 3 pounds, 12 ounces mozzarella cheese, thinly sliced

Combine eggs, cottage cheese, 1 quart parmesan cheese and parsley. Mix well. Refrigerate.

Cook noodles until al dente.

In 5 12-by-20-by-2 1/2-inch steam table pans layer 1/2 quart meat sauce. Top with noodles, flat and in rows. Cover with 3 cups filling, 6 ounces mozzarella cheese. Top with noodles, flat and in rows. Cover with 1 1/2 quarts meat sauce. Sprinkle with parmesan cheese. Bake at 350 degrees until top is bubbling, about 1 hour. Let stand 20 minutes before cutting to allow cheeses to firm. Cut into pieces, 5 lengthwise and 4 crosswise. CHILI CONQUISTADOR (100 servings) For chili sauce: 24 pounds ground beef 2 pounds onions, chopped 9 cloves garlic, minced 1 1/4 cups chili powder 1 teaspoon red pepper 9 tablespoons salt 2 1/4 gallons crushed canned tomatoes For rice: 5 1/4 cups rice 1 2/3 tablespoons salt 2 tablespoons salad oil or shortening, melted 2 3/4 quarts cold water For assembling: 2 gallons your favorite corn bread batter

Cook beef with onions and garlic in its own fat until beef loses its pink color, stirring to break apart. Drain or skim off excess fat. Add chili powder, red pepper, salt and tomatoes to meat mixture. Stir until blended. Heat to simmer and set aside.

Add rice, salt and salad oil or melted shortening to water. Bring to a boil. Stir occasionally. Cover, simmer 25 minutes. Combine rice with chili mixture, blend well. Place 2 3/4 gallons of mixture in each of 2 18-by-24-inch roasting pans.

Prepare corn bread batter. Spread 1 gallon corn bread batter over chili mixture in each pan. Bake 45 minutes at 350 degrees or until done. Cut into pieces, 9 lengthwise and 6 crosswise.