What we will see on the river, John Cronin tells me, is the past, present and future--"what we have been fighting against and fighting for." The against comes first. On a late-spring morning full of sunshine and blue water, we push off in a 26-ft. sportfishing boat used by Cronin's watchdog group, Riverkeeper Inc., to patrol the Hudson. Heading north, about 40 miles north of Manhattan, we see the Lovett Power Station on the west bank. The old, dark, brick coal-, gas- and oil-burning tangle of structures looks like a giant outdoor furnace. Beside it is a quarrying operation that once dumped a load of sand and gravel from a conveyor belt into Cronin's boat while he was in it, to discourage scrutiny.

"We were so dumb," he laughs. "We watched the belt swing over our heads, never suspecting what they were going to do."

On the east side is a plant that uses gypsum to make Sheetrock and that, thanks to Riverkeeper, has done a cleanup. Just beyond it rise Units 2 and 3 of the Indian Point Nuclear Power Plant. Two mosquelike domes flank a sky-high smokestack painted in red and white stripes. It looks like a lighthouse that has been converted into a festive nuclear missile. Beyond that, at Charles Point, lies a garbage-burning plant, which turns trash into energy.

All the plants, says Cronin, are located in exactly the wrong part of the river--the broad, shallow heart of the estuary that serves as a nursery for striped bass, bay anchovies and American shad. The plants suck in water with great force; Indian Point alone uses a million gallons a minute. Fish small enough to slip through the meshes are killed at once. Larger fish are impaled on the screens and killed or maimed. Riverkeeper has forced Indian Point to install $25 million worth of fish-saving equipment, and in 1994 the group successfully sued to make the Environmental Protection Agency set official safety standards for power plants.