The current in the Edgartown harbor has changed again.

It has been three years since the Norton Point opening connected Katama Bay to the sea, and the water movement through the harbor has gained another measure of unpredictability: currents running through Edgartown harbor are far greater than tidal.

Plus, the three years of increased current has changed the way boaters use the harbor and the way bathers use the beaches.

Edgartown harbor master Charlie Blair said the current is still going at times as fast as four knots, slightly less than two years ago.

But what is getting everyone’s attention is the movement of sand. There is less beach at Chappaquiddick Point and less beach near the Edgartown Lighthouse.

At the Edgartown Lighthouse where for many years the point was moving into the deep waters of the channel, towards the Chappaquiddick Beach Club and constricting the channel, it has since retreated. There were talks of bringing in a dredge to trim the growing real estate. It won’t be necessary. Mother Nature and King Neptune have moved it without a shovel.

Breach creeps toward Chappy, changing beaches, currents in harbor. — Michael Berwind

Capt. Robert Gilkes, 64, who works as a captain on the Chappaquiddick ferry, has monitored the currents and to him there is more water moving between Memorial Wharf and the Chappaquiddick Point. There has been scouring and it has changed the behavior of the currents. “I can’t confirm this, but judging by the erosion at the lighthouse and the submerged bank, where it drops near the ramp, it is deeper. The volume of water is not restricted.

“It still gets harried. It will be wicked when there is a full moon,” Mr. Gilkes said.

At the other extreme Edgartown harbor is experiencing something that hasn’t happened in years: There is slack water and it can last as long as 25 minutes. At that time the water isn’t moving; whether the tide is rising or falling is hard to tell.

Tide and current are distinctly two different water characteristics in Edgartown. It used to be that when the tide was rising, water would be coming into the harbor as it does at Cape Pogue Pond. When the tide is falling, water is leaving the harbor.

But since the opening, the current moves in either direction when the tide is rising or falling.

Generally speaking, Mr. Gilkes said, the tide doesn’t seem to reach the high tide mark regularly or the low tide mark regularly.

“One of the effects we see is that low tide at the ferry, doesn’t really reach the low tide level, because the two-hour lead at Katama Bay is already bringing the flood,” Mr. Gilkes said. “We are not getting the high and low tides that used to be routine,” he said, storms being the exception.

Mr. Blair said he has seen extreme high tides he hasn’t seen before.

Mr. Gilkes said the trip to Chappaquiddick from Edgartown is longer. A round-trip used to take four to five minutes. “Now it easily takes eight to ten minutes,” Mr. Gilkes said.

Mike Creato, a pilot for Classic Aviators at Katama, gets up in the air a lot. He said the Norton Point beach opening continues to move east towards Chappaquiddick. “It seems like the Edgartown side has closed in a bit. It did that before and was pushed back,” he said. An ocean storm can undo the changes as easily, so the progress doesn’t appear permanent.

“The central channel is still very deep,” Mr. Creato said of the Katama Bay opening, but he added: “The bay is very shallow.

“The channel changes all the time,” he said.

There may still be uncertainty about how the increased flow has changed the rising and falling tide and currents, but there is certainty below the surface.

Heidi Leonardo, of Oak Bluffs, is a professional diver. To her, what lies below the surface is starkly different from three years ago.

“We’ve seen with increase water flow, you don’t have the dead bottom there was,” Mrs. Leonardo said. “There may be a few places that are anaerobic, but the underwater life has improved. With the increased flow of nutrients, we have better quality of life on the bottom. I am seeing more coral and more fish. It is interesting.”

And out of the movement of water, the bottom has been cleansed of silt. Mrs. Leonardo said she found old bottles that go back decades, lying on the sand.

“The opening has flushed all the silt out of the harbor,” she said. She and her husband, Joe, run Vineyard Scuba, an Oak Bluffs retail business.

The harbor master thinks the current flow has hurt harbor business. “We are losing revenue because the break remains open. We pray that it will close down, as it has in years past,” Mr. Blair said.

Sailors without an outboard or an auxiliary motor can be at the whim of the currents. “I had to put a warning in the harbor Web site, and it was reported in sailing magazines.

“The scouring has been done. The cleanup of the harbor has been done. Now we are waiting for the breach to close,” Mr. Blair said.