Beaches on the eastern half of the island, where most of the condos and inns are located, can be busy. But from about the halfway point west the shoreline is virtually deserted much of the spring and summer. Many days you can fish for hours without encountering another fisherman, though you will have to watch your backcast for occasional joggers and shellers. One reason for the dearth of anglers, of course, is that snook fishing in May, June, July and August is strictly catch-and-release. Many bait and spin fishermen do not try for the linesiders-excellent eating fish-when they cannot keep them. For fly fishermen it presents a great prospect: lots of action and little competition.

I like to eat fish as well as the next guy and, in season, keep an occasional snook for dinner. But I agree with Dave Westra when he says, "I always feel better putting one back than putting it in the freezer."

Fishing begins to pick up along the beaches when the water temperature reaches the mid-70s and really gets going when it hits 80. During the peak months for beach fishing-May through September-snook can be caught on all tides but the best tides are usually outgoing from about half tide to just before dead low and incoming from about one hour after low to half-high.

The silvery-white snook seem to disappear in low light so the best morning sight fishing is usually after 8:30 a.m., when the angle of the sun is not too low to the water. Likewise, in the evening it starts getting difficult to spot the fish about an hour before sunset.

Most beach snook are between 18 and 28 inches but on early summer evenings the big females cruise the shoreline, often followed by three or four smaller males. One night I chased a three-footer 300 yards down the beach, repeatedly dropping the fly a foot or two in front of her. She did not spook or take, just kept swimming along the shallows, belly scraping bottom and dorsal fin flexing above the surface. Finally she turned toward the Deceiver, but a little 20-inch male grabbed it away from her.

Some anglers make the mistake of wading right out into the water as soon as they get to the beach. This can cost them fish. Often snook cruise just off the first shelf, inches from shore and in less than a foot of water. Fishermen should approach the water warily, standing back from the shoreline and looking left and right for movement or shadows.

Some days, even entire weeks, can be frustrating. When the wind comes up out of the south or southwest the churning surf turns the water to coffee, eliminating the sight fishing. More than once I have been outfished by an osprey.

As with any fishing, the key is to take advantage of the good times. One Easter my brother-in-law and his best trout-fishing buddy came for a week of beach fishing. The first morning was calm and we saw scores of cruising snook. Assuming it would stay like that, they went off to play golf in the afternoon. But that night the wind swung around to the southwest and stayed that way for five days. They caught a few snook blind casting in crashing surf but saw no more.

Most beach fishermen use an 8- or 9-weight rod. But, partly because of joint problems, I prefer a 7-weight. It is easier on the casting arm and, in very calm, clear water, the softer-landing line can make a difference between spooking or hooking a fish.

When the Gulf is clear along Sanibel, what you see is what you get. But, as anywhere, blind casting is a game of uncertainties. Diving pelicans and terns or skittering baitfish may give hints where the fish are, but in general it is cast and hope. The best bet is to stand near water's edge and cover 180 degrees with your casts, from parallel to shore to straight out.

Casting to snook in the shallows generally calls for a floating line. But blind casters working the shoreline trough should consider switching to a sinking or sinking-tip line. Some of the water in fly-casting range can be four or five feet deep at high tide and an unweighted streamer may not get down to where the fish are.

And it is never certain what the fish will be. Though snook predominate, you may pick up seatrout, pompano, jack crevalle, ladyfish, Spanish mackerel or even an occasional redfish. Summer is also when the big schools of stingrays move in. I prefer to wade barefoot, but from June to October, it is a good idea to wear wading boots in turbid water.

Clear water calls for at least a 9-foot tapered leader with a minimum 12-pound tippet. In addition, always use a shock tippet. I pooh-poohed the idea when I first started snook fishing, thinking 20- to 26-inch fish were unlikely to break 12-pound test. Then I lost three fish in a row. They abraded the line as fast as I hooked them. Snook have sandpaper-like teeth that will wear through anything lighter than 20-pound test faster than you can land them. I like 30-pound-test fluorocarbon. You may spook a few extra-wary fish but at least you will land many of the ones you hook. Remember to check the shock tippet for abrasion after every fish or you may lose the next one.

A loop knot is best for attaching flies because it allows them to swing and move more naturally than a clinch knot, especially with the stiff shock tippet. My favorites include chartreuse-and-white or yellow-and-white Deceivers, Clousers in similar color patterns and a no-name streamer I call Norm's Crystal Schminnow: a pearly white crystal-chenille body with a white marabou tail and burnt-monofilament eyes.

Westra uses similar flies, and also stresses the size factor: "I like small Deceiver-type patterns, meaning nothing bigger than a 1/0 hook," he says, "and they could be as small as a No. 2. And No. 2 Clousers are ideal."

The Deceivers and Clousers approximate the greenbacks and shiners that school up along the summer beaches, but the Schminnow resembles nothing in nature. It is part shrimp and part minnow, with maybe a hint of sand crab. Though unprepossessing, it is the only streamer I have seen snook actually come out of the water to chase.

The shore has many moods and surprises: crystal shallows fading to azure blue depths; thunderous breakers, roiled and viscid; dolphins, pelicans and cormorants; ospreys crash-diving the swells to snatch a fish.

Last year my friend David Bryer, an avid trout fisherman from Billings, Montana, flew down in quest of his first fly-rod snook. It was the second week in June, the height of the early snook run. We fished the first morning in near-perfect conditions: little or no wind, glass-clear water, scores of snook cruising the shore. But none of them would hit our flies.

After an hour and a half David was still fishing intently but I knew he was fascinated yet frustrated. We finally took a break from picking out specific fish and began casting Clousers into the trough, where we could spot only shadows, or nothing.

David worked his way west along the beach and a few minutes later I heard, "Got one on!" and turned to see his rod doubled over. I hurried down the beach with my camera and after the fish made two good runs and three jumps he slid it up on the shells and sand, a shiny silver 22-incher. The ice was broken and now we could relax.

"Nice fish," I said.

"Yeah, but I thought he was bigger. Man he hit hard. They've really got some power."

The next day he landed a 26-incher, a great flyrod surf snook any day. "I cast to him and saw him hit. Then man, he really took off. He jumped eight times," he said.

I asked David to move out into the Gulf 20 feet or so and pose while releasing the fish. While I was shooting the photo, off to his left I saw something break the surface.

"That looked like a manatee snout," I said. "I've never seen one on this side of the island." Then a few feet from that spot three good-size jack crevalle shot out of the water. I looked closer and a 10-foot hammerhead flashed after them, dorsal knifing through the surface.

"Get out of the water, David," I said. "Now."

He pushed away the snook and waded quickly to shore. Afterward, we joked about the excitement of snook fishing on Sanibel.

Northerners tend to think of Florida as having two seasons: hot and hotter. As a native New Englander who later lived overseas, also in a northern climate, I was once among them. But I have learned to cherish the subtle turning of Sanibel's yearly cycles. Summer's tropical sun, towering cumulonimbus and the drenching downpours of late afternoon. The first cool fronts of autumn, sweeping down to banish the mosquitoes and humidity. The rare winter blows, churning the Gulf to froth and strewing the shore with shells (the same Gifts from the Sea Anne Morrow Lindberg found on nearby Captiva).

And each spring, when the old leaves fall and the first blossoms show on the sea grapes and black olives, when the Gulf winds die down to a whisper and the Australian pines stand still against the sky, again I will walk the beaches in search of snook.