For about the third time of the morning, the overheat alarm on the outboard engine shrills -- sweet music to my ears, and, I suspect, also to Mike Naylor, who's been working and hoping for several years to see just this problem.
The "problem" is that we're running through underwater grasses on the Susquehanna Flats near Havre de Grace -- grasses so thick they occasionally clog the engine's cooling water intakes. Other times they wrap up the propeller, slowing us significantly.
This was a fact of life when cruising vast regions of shallow, grassy waters throughout the entire Chesapeake when I was growing up in the 1950s and 1960s. The upside of so much grass was huge, of course -- clear, naturally filtered water that was a haven for crabs, fish and waterfowl.
In the 1970s, pollution hit the grasses hard, and they have never returned to anywhere near their former glory.
But recently, across several thousand acres of the flats, great shallows formed by sediment deposited where Pennsylvania's Susquehanna River meets tidewater, a remarkable comeback has been building.
Wild celery, coontail, redhead grass, pondweeds, naiads, water stargrass with its showy golden flowers -- all these and other species that we lump under the uninspiring rubric of SAV, or submerged aquatic vegetation -- have been springing to life in abundance and diversity not seen for decades.
Naylor, who heads Maryland's restoration efforts for such underwater meadows, estimates that grass coverage of the flats has grown from about 5 percent in 1996 to 50 percent or more this summer.
"I've never seen such a huge area where practically all the shallow water habitats are covered in aquatic plants like this," he says.
And it strikes me that Naylor, 35, the state's SAV restorer, was only 5 or 6 when the grasses crashed. Vivid memories for me are history for him.
That's one reason I'm so glad to see and publicize this comeback. Everyone who's under 35, or has moved here since the 1970s, has little direct experience with the grassy ecosystem we'll need billions of dollars and big changes in behavior to restore.
Naylor is muted in his assessment of how today's public will respond to an explosion of bay grasses. "A lot of the calls we are getting now are complaints from boaters about `nuisance' grass," he says.
(Hunt those whiners down like SAV-chomping mute swans, I advise.)
Naylor was not content with the memories of old fogies. The Department of Natural Resources biologist assembled aerial photos from the 1930s and 1950s. Taken primarily as federal surveys of the region's farmland, they gave him an estimate of what the grasses were once like.
He knows from this that the flats aren't back by any stretch.
Still, it's a day to revel in progress. Everywhere the clear water is flecked with white dots, the pollen of wild celery.
Off Elk Neck State Park we snorkel through beds of celery and redhead grass so thick you must part them with your hands and kick hard to move along.
Head down, you can get lost in the sun-streaked jungles of lush underwater greenery.
The good news on the flats comes from clearer water than the region's seen in decades. Enough light is getting through for the grasses to thrive.
That's a tribute to Pennsylvania's controlling phosphorus from sewage and farms upstream. The state isn't doing enough for a full comeback, and not nearly enough to control nitrogen, which pollutes the saltier waters down the bay.
But progress is not always clear. Witness an area of about 30 to 40 acres along the Havre de Grace side of the flats. It is blanketed with the nastiest-looking mats -- up to a few feet thick -- of dense, gray-green algae any of us have seen.
For several years, watermen have noticed scattered occurrences of this "macro" algae (as opposed to the floating "micro" algae that have traditionally clouded the bay's waters).
It has forced fish netters and crab potters to move their gear from traditional fishing grounds. "It's put a lot of us out of business in the upper bay," Pip Pratt, a waterman from North East told the Waterman's Gazette recently.
Scientists say it's possible, based on water-quality comebacks in places such as Tampa Bay, Fla., that the ominous algae may be an intermediate stage on the way to healthy meadows of native grasses.
Or maybe not. No one's sure yet. I recall that when water quality improved on the Susquehanna around Harrisburg years ago, black flies began to breed for the first time in decades. Ecologically, it was progress. But it was a tough sell to a fly-swarmed public.
It is humbling to realize how much we know about what the bay and other ecosystems look like as they degrade and how little experience we have had with the path to restoration.