Last Wednesday, under bright sunny skies and light seas, Dan Farren completed his 1,500th crossing of Nantucket Sound for the Falmouth-Edgartown ferry service. Captain Farren, 63, began working the run in 2001. For the crew and many passengers on the ferry Sanderling, it was a routine trip. But for the captain, it was a special notation in a little notebook he carries in his shirt pocket.

Mr. Farren didn’t start the job to count every single one of his ferry trips. While there are many ferry captains who serve the Islands, who would be able to tell how many trips they had taken?

“You are supposed to keep track of your sea time,” he said. He took that assignment a little more conscientiously than most. After all, he had worked for 28 years as a school teacher in Falmouth. “I keep a diary. I keep a log,” he said.

Somewhere around his 1,000th run, customers on the ferry asked Mr. Farren how many trips he had taken. He said he went back and counted. And he has been counting precisely ever since. Ferry service runs from Memorial Day weekend through Labor Day. In those earlier years, for many summers he taught sailing for Community Boating in Boston.

In these past 11 years, Nantucket Sound has been his workplace; it is the weather and seas that are most varied. It takes about an hour to make the crossing. From dock to dock, it is 13 miles. The two ferries on the service, either the Pied Piper or the Sanderling, will go about 15 to 16 knots.

Though enclosed by the boundaries of two Islands and the southern shoreline of Cape Cod to the North, Nantucket Sound is a lively sea, especially during the worst of storms. In the interest of passenger safety, Mr. Farren said they will shut down ferry service when it gets too rough. “The boat can take it, but the people get sick.”

This summer, the captain said he saw an amazing weather phenomenon. Visibility dropped to just 150 feet, in a short time during a summer thunderstorm. The sky simply opened up and water came down.

There have been other memorable weather events, like one pitch-dark night with fog in Edgartown, worse than any other time.

When he is not captaining for the ferry service, he fills his days off being a captain of a whale watching boat, Captain John and Son IV out of Plymouth. There is no mistaking this captain’s pleasures; he loves being on the water and being a bit of a school teacher in what he does.

Mr. Farren is an avid advocate for safe boating. He is the top division commander for the Cape and Islands Coast Guard Auxiliary. It is a volunteer position, in which he oversees the actions of over 200 volunteers from Nantucket to Woods Hole.

Part of the impetus to lead comes from his experience on the water, of watching boaters perform well and badly. He said that he is often amazed at how boating safety is a low priority for some. From time to time he will shake his head when he sees an overloaded dinghy in which no one onboard is wearing a life jacket. Or worse, little children on small boats without a life jacket.

One of the most bizarre experiences he had with the ferry service was in his first year, when he worked as a mate.

While the boat was leaving Memorial Wharf for Falmouth, a late passenger ran and jumped over the water to get aboard the vessel. “He jumped onboard and then held on to the railing,” Mr. Farren said.

But that isn’t half the story.

Once onboard, the passenger bought his ticket and then revealed that he wanted to go to Chappaquiddick.

Mr. Farren still remembers making a crossing in the fog and discovering six kayakers out in the middle of the Sound paddling over to the Hedge Fence buoy, which is considerably far offshore from Oak Bluffs. He still wonders to this day whether they knew where they were.

More recently, he recalls a woman in a dinghy caught in the channel between Edgartown and Chappaquiddick with her outboard motor not working, having to row back to port. Murphy’s Law seemed to rule that boating moment, and the current wasn’t helping her. He said he called the Edgartown harbormaster to share his concern. “I’ve got all the harbor masters on speed dial,” Mr. Farren said.

Even when he isn’t working, Mr. Farren loves to be on the water. The day after completing the 1,500th run, he took a friend out in his boat and went fishing at Hedge Fence Shoal. “We caught black sea bass,” Mr. Farren said.