IN WASHINGTON the other day the President met with the Russian ambassador, the State Department announced aid for Zaire, the sentence of G. Gordon Liddy was reduced and Jim Malloy, 29, sat on the banks of the Potomac by himself, two fishing lines in the water, a fish hooked on both, both snagged on rocks.

"They hung me," Malloy said. "They hung me, that's what they did. They do that to you. They go under a rock. Here I am sitting with fish on both lines and I can't bring them in." He pointed to the line. "See that line?" The string jerked. "Look at that. Just look at that."

The time this was happening was about noon and the place was just above Fletcher's Boat House. There, the river slows and starts to pick up the pace it maintains all the way to the bay.The sun was high and hot and the boats floated lazily among the rocks. Mallory, chunky but strong and wearing shoes that he kept unlaced, flung his legs over the bank and said he could sit like that all day. It was Washington's first really warm day.

There is no accounting, really, for what the first warm days can do to you. There was the motorbike cop I saw in the park. He came up behind me on the trail and it was clear right off that he did not belong in this park. He was a D.C. cop and this was a federal park, so when he saw me, he sat erect in the saddle, set his jaw in proper policeman fashion and scanned the woods as if he was looking for someone. He passed me once, made a wrong turn and then had to pass me again. This time, he gave up the act. He smiled like a guilty kid and said, "nice day for a trail ride."

The weather has brought me down to the river to learn about fishing. What I wanted to know, more or less, is why people do it. I have tried once or twice and I remember as a kid going down to the ocean and sitting on the rocks, casting a nail tied to string into the water. Once, I think, I caught a crab and once, I know, a friend came up with a fish. He must have had a hook. Anyway, we put the fish into a cookie box and waited for it to die. Every once in a while, we'd open the box and the fish would flap around and we would slam the cover closed. I can still remember the way that fish looked at me.

So I sat down next to Malloy to learn. He was a good teacher. patient and informed, who told me why some fish are called suckers and how a catfish will stay alive even if its skinned. He told me he is a photographer for the Navy, a native of Virginia and something of a fishing junkie. This was his third straight day. All the time he talked, he kept an eye on the snagged lines.

"I've got them, but it's hung," he said. "I'll just try and wait. See what happens." He looked at me and laughed. "I believe you gave me bad luck," he said. "Believe you gave me bad luck . . ." Malloy explained fishing. He called it sport and said that the way he saw it he was sort of matching wits with fish. It was a contest. A battle to the death. Never know what a fish would do - how they rob your bait and take your line into the rocks and how you got to know just by the feel of the line if you got a bite.

"He's playing with it," Malloy said, pointing to one of the lines. "He's just playing with it. Yesterday, I took in a fish that had a hook half way down his throat. He had my hook and he had this other hook. I was trying to figure out yesterday why a fish with a hook halfway down his throat would take another hook."

I told Malloy that my father was never a fisherman. He went once or twice with a man named Bernie who lived down the block and owned a small boat. Someday, Bernie said, he would take me. One day Bernie went out in his boat and never came back. The boat capsized, my neighbor drowned and my father never took me fishing. That's probably the only way you learn, I said - from your father.

Malloy agreed. He said he had learned from his mother and father and he was grateful to them for the lessons. The more he thought about it, the more he had to conclude he owed his parents quite a lot. They had thought him fishing and fishing was something he loved. "If it hadn't of been for them, I wouldn't be on this river today." he said.

Well, there were kids all up and down the river bank, but there were none with Malloy. So I guessed he had no children and I guessed he wasn't even married. Wrong on both counts, he said. He had a wife and together they had a boy, but the boy would not fish. "He's afraid of falling in," he said, "He's afraid of river banks."