A whale of a time in Cape Cod

It looks like the Loch Ness monster has surfaced, and she’s blasting a spray of water 10 feet high, drawing cheers from three boatloads of tourists.

Unlike Nessie, though, this sea creature doesn’t seem to mind the attention. A 45-foot humpback whale named Nile, she’s nearly as big as an 18-wheeler. And she’s putting on a show.

She flips up a notched fluke, or tail, that’s as wide as a car, then dives deep, creating a cloud of bubbles above her to corral the small fish she eats. When she surfaces again seven minutes later, cameras click and passengers aboard the Hyannis Whale Watcher Cruises boat whoop and holler.

Here on Cape Cod, whale watching ranks right up there with beach combing, swimming and lobster roll eating. We’ve done all three on our weekend visit to this vacation mecca a few hours from Boston.

The seas are so calm today that we can hear the raspy puffs each time Nile exhales. Apparently you can smell whale breath, too, if you’re close enough. We are not, thanks to strict regulations that govern how close whale-watching boats can get to these beautiful and endangered mammals. The on-board tour guide explains all this, and doles out some other interesting tidbits along the way.

Fins, for one. Humpback fins are splotchy white, and they glow neon green through the water. They’re up to one-third of the animal’s length, the largest of any whale. In Nile’s case, they’re 15 feet long, and covered with barnacles.

And those flukes? They’re like fingerprints. The grooves and mottling are unique to each animal. It’s how researchers identify and keep track of individuals — and how they know that Nile was born in 1987 and has been migrating between here and the waters surrounding the Turks and Caicos Islands ever since.

Our four-hour excursion started at 2 p.m., taking us out of Barnstable Harbor and past Sandy Neck, where a group of revelers on the narrow spit hailed us with waves, then turned to show us their bare behinds. It took an hour to reach the Stellwagen Bank National Marine Sanctuary, where the more interesting critter watching commenced.

Here, an upwelling of current pushes up the detritus that fish feed on. That draws in whales, which lure in the tourists. Our 130-foot boat featured two outdoor decks, indoor air-conditioned sitting space, bathrooms and a snack bar that serves Whale’s Tale beer and whale-shaped lollipops, among other things.

I’d worried we might not see any whales, but I haven’t been disappointed. Besides the humpback, we soon spot a smaller minke whale and a tiny otter, who gapes up at us with round eyes.

Passengers sometimes see finback whales, too, which stretch up to 72 feet long, and North Atlantic right whales, which are nearly as big and critically endangered.

“I don’t think I’ve been skunked yet, and I’ve been on the boat six weeks,” says Lauren Duehring, an intern at Whale and Dolphin Conservation, a nonprofit agency that works to protect the seafaring mammals and educate the public about them.

The trick to finding the animals, she says, is scanning the water for odd-looking shapes. Whales can blow mist up to 30 feet high, and that makes them visible up to a mile away.

The humpbacks, she explains, migrate each spring from waters near the Turks and Caicos, where they mate and reproduce. When the babies are just a few weeks old, they head 1,500 miles north to fatten up for the following season. The babies gain up to 100 pounds a day here, eating small fish like mackerel and herring.

I know the feeling. In the past day we’ve already made the requisite stop at the Sesuit Harbor Cafe for lobster rolls (we called ahead, picked them up and drove them out to a nearby beach to watch the sun set while we noshed) and Buffy’s Ice Cream in Chatham, which has the most mind-blowing ginger ice cream on the planet.

The whales, though, need the extra blubber. After four to six months here, they’ll migrate back south, where they can lose several hundred pounds a day and don’t have such a readily available buffet of food.

They face plenty of dangers along the way.

Entanglement is the leading cause of death among these whales. Even Nile, known to have given birth to at least four calves, got entangled in fishing gear in 2001. Rescue workers were able to loosen the ties, and eventually she worked her way free from the gear.

We get a last glimpse of Nile’s arching back before she raises her fluke one final time.

I know it’s silly, but I can’t help it. I applaud as she disappears under the water.