MY FRIEND ROSS NEILL is looking grumpy, and I'm to blame. Five of us are about to get on a small fishing boat—Ross, me, his parents, and our guide—but we've just realized that we don't have fishing licenses, so we'll have to change our plans.

We're staying together on Sanibel Island, Florida, and I should have made sure everybody bought licenses there this morning. We were running late, though, and I figured we could get them at our destination, an isolated waterfront town an hour to the north called Pineland. Alas, Neptune has been cruel. There are docks and boats and even a fishing lodge here, and the whole shebang faces a huge swath of inland salt water that's teeming with redfish and snook. But there's no bait shop.

I try not to look at Ross as the news sinks in that we'll spend our first day (of two) exploring barrier islands, collecting seashells instead of throwing hooks. He's 15, not 50. This does not represent an upgrade.

Our guide, Rogan White, the 25–year–old son of editor at large Randy Wayne White, tries to make the best of it, taking us several miles out to an island called Cayo Costa, where we hit the shore for a morning of, um, extreme beachcombing. Ross says "Goddammit!" when his feet get wet and is bored by a sign that says the island has a population of wild hogs. (Unless they come out and devour me, what good are they to him?) Rogan takes us to a tide line where there's a long, thick band of unpicked shells, cheerfully declaring, "This beach is loaded."

Ross isn't buying it. While his mom and I go for a swim, he sits with his dad near scruffy undergrowth at the back of the beach, a blond, blue–eyed hermit crab huddled inside a Mariano Rivera T–shirt.

I have to wonder if something else is wrong. Ross and I are old outdoor buddies, and there's usually more zest to his negativity. Later, I ask his parents—Tracey Harden and Michael Neill, a Manhattan couple—what's up, and they confirm that his bad mood isn't about the blown fishing day. The kid has more serious things on his mind: In a couple of weeks, he's scheduled for a risky surgical procedure that has him terrified.