Famed ornithologist Forrest Gump said, “Birding is like a box of chocolates. You never know what you’re going to get.” And with that philosophical observation ringing in our ears, a boatload of birders set out to sea under frigid December moonlight to go find some chocolates.

Last month, Rich MacDonald, owner of the Natural History Center in Bar Harbor, partnered up with Diver Ed to let birders tag along on a winter scuba diving adventure. Diver Ed’s Dive-In Theater boat trips off Acadia National Park are popular with visiting families all summer, but Ed is apt to conduct a few charter dives in winter, too. So we jumped on board one charter to see what birds were lurking offshore.

It was before dawn and temperatures were below freezing as the Starfish Enterprise pulled away from the pier in Northeast Harbor. To stay warm, I wore my entire wardrobe. Now I know why the castaways of Gilligan’s Island brought along all of their clothes on a three-hour tour.

A winter boat trip is mystery and fantasy. On land, experienced birders have a pretty good idea of where to go and what they might see when they get there. At sea, the weather, winds, tides and wandering fish can attract the birds or repel them. The sea can be alive one day and dead the next. So we hugged the rail and squinted into the rising sun, filled more with hope than expectation. We quested for unusual members of the puffin family, such as dovekies and thick-billed murres. We salivated over the prospect of a skua. The great skua nests in Iceland, Scotland and Norway. The south polar skua nests on barren ground in the Antarctic. Both wander widely at sea and can show up in Maine waters. They are closely related to the three jaegers: parasitic, pomarine and long-tailed. All rely on kleptoparasitism — a 25-point Scrabble word that means they get most of their food by stealing it from other birds, generally gulls and terns. Though none of these desired birds is likely, if there is going to be any food stealing, it’ll be at Mount Desert Rock.

Our destination is a small island located about 20 miles southeast of Acadia National Park. This 3-acre rock is just roomy enough for a lighthouse, a light keeper’s cottage, a few summer researchers and a whole lot of gulls, cormorants and seals. The seals were particularly abundant as we pulled up on the southern side of the island to anchor and send our scuba divers overboard. Maine has a lot of places where harbor seals can be seen easily. Gray seals are much bigger and less common near shore. On this particular day, both species covered the rocks. Neither seal seemed to be overly nervous about our unexpected appearance. In fact, the divers reported finding them to be in a curious, almost playful mood under the surface. Rather than wrap myself in rubber, strap on a tank and jump into an icy brine, I’ll just take their word for it.

Maine is the southernmost limit of great cormorants in breeding season, but they’re easy to find only in the winter months. They are slightly larger than double-crested cormorants and the adults show white cheeks. On this day, the greats were plentiful on Mount Desert Rock, too large to be concerned by the marauding peregrine falcon that sat on the light keeper’s cottage roof. We counted 50 altogether. The day’s highlight, though, was the multitude of Iceland gulls on the island. With enough dedication, you can usually find an individual Iceland gull along the Maine coast in winter, but it was startling to be swarmed by them. The group tallied 14 Iceland gulls, which look much like our common herring gulls but lack the black wingtips. The glaucous gull is another white-winged gull that is an uncommon winter visitor. It is nearly as large as a great black-backed gull, the world’s largest gull. We glimpsed only one glaucous gull, which came close to the boat just long enough to investigate our ruckus and then ambled off with profound indifference.

While we didn’t spy any of our fantasy birds, we feasted on a lot of chocolates. I’m told we counted 1,509 individual birds representing 30 species. I wouldn’t know. My fingers were too cold to count past 10.

Bob Duchesne serves in the Maine Legislature, is president of the Penobscot Valley Chapter of Maine Audubon, created the Maine Birding Trail and is the author of the trail guidebook of the same name. He can be reached at duchesne@midmaine.com.