I squinted across the river. I was directly on the line between the two markers, the dead tree trunk in the Virginia bank and the two stumps on the Maryland bank, and just downstream from the point of Ruppert Island. I dropped my feet. They dangled beneath me. I swam a few more strokes and dropped my feet again. Success. They touched on the slimy rock I was looking for. I stood and rested. The water was up to my neck. The river was high for mid-summer. It was warm, almost unpleasantly so. A small leaf caught in a bit of scum slowly floated by me.

I eyed the woods an the opposite side of the river and thought about the spies, complacent in the stronghold of the C.I.A. at the top of the bluff. They probably needed an invasion. I left my rocks and started across the river, doing a lady-like breast stroke -- my head high out of the water. The snake that lived under the float swam the same way -- head up, eyes open, wiggling slowly along. "Be careful not to get your head in. The water is so dirty, we don't want you to get another earache." My father, though, doesn't believe the pollution myth. "The latest Government test shows the river is almost clean enough to drink just as it is." He should know.

I sank, feet first, down to the colder layer. I opened my eyes. It was green. Green as if I were standing in a dusty wine bottle. My hand, six inches from my face, was a white blur. I moved it further away and it became a part of the green nothingness. The bottom of the river wasn't quiet. Something -- the rocks or fish -- was softly rumbling. I shut my eyes and came back to the surface. I put my fingers in my ears to shut out the sound and frog-kicked along just below the surface. When I came up I found I had swum in an arc and was facing the wrong bank. I turned around and started off again, aiming at a tree slightly upriver of where I planned to land. Maryland was getting farther away. The people on the dock were little. Virginia still looked no closer than it had.

I swam on my back with my eyes shut, keeping the sun over my left shoulder. An airplane roared overhead. I used to think it odd that so many planes should fly along my river, but now I knew it was planned that way. The river is supposed to absorb the sound or something. Maybe it wasn't the rocks and fish but old airplane roars that made the bottom of the river so loud. The brown ducks decided to leave as I came close. Flapping their wings furiously, they left, trailing their feet splashing through the water.

I was definitely making progress. As I neared the shore I felt the current becoming stronger around me. I was a shipwrecked sailor struggling for my life. I swam harder, desperately fighting the tide, the treacherous undertow, and the surf that could dash me on the jagged coastal rocks. I was tired. My legs dropped. They hit mud. The water was about three feet deep. End of the shipwrecked mariner. Now I had to decide whether reaching the shore was worth a wade through the knee-deep Potomac river mud. It smelled terrible. I half crawled, half swam, trying not to sink in. People throw all sorts of things into the river. I didn't want to land on an old tin can. I hauled myself out of the mud. I sat on the bank and looked up the bluff in the direction of the C.I.A. The guards would have been awfully surprised if I had hiked up the hill and laid siege to the building, but I didn't.

I picked up a sycamore leaf as proof I had been there. I could carry it back in my teeth to show the natives. Or better yet, I could pick a whole branch, take it back, and start a colony. No, I'd just take one, an unimportant, somewhat used one. I decided it was matches. I couldn't get them wet. Forgetting about rusty beer cans in the mud, I waded out. I sank in up to my knees. Dirty bubbles rose from the mud in the streams. Further out the bottom was sandy. I walked out beyond the current and started to swim, holding the leaf above me. I looked across the river to the island I had started from. A thread of smoke was rising across the trees. The island was populated -- my family. They had started a fire. They wouldn't need my matches. I let the leaf go and swam faster. They were probably starting lunch.