As a Coast Guard crew patrolled the water in a routine mission Wednesday, they spoke among themselves about the recent whale sightings in Boston Harbor.

“One breached like 5 feet off the port bow,” said Petty Officer Taylor Reaser, who saw two whales by the Harbor Islands on Tuesday around noon. “I could have reached out and touched it. It was really, really cool.”

Alongside his colleagues, Reaser set up a perimeter around the whales Tuesday, protecting the large mammals while they swam in the heavily-populated harbor. Reaser, who loves his work protecting humans on the water, said he felt a special pride watching over the wildlife and keeping them safe from boaters.

“I’d never seen whales before, but these were breaching all over the place” said Reaser, who grew up in Ohio. “Maybe in a video or an inflatable one in a pool, but never in person.”

Humpback whales, which often grow to around 50 feet as adults, have been spotted several times in the harbor since Sunday, including as recently as Wednesday morning. On Tuesday, the Boston Harbor Cruises tweeted out a video of the whale, saying “Have you heard the news?” State Department of Conservation and Recreation officials also shared a video of a humpback whale that was seen leaping from the water near the Deer Island wastewater treatment plant.

These unusual sightings come from the humpbacks looking for a snack in warmer waters closer to shore, experts said.

“The whales are following their food,” said Allison Ferreira, a spokeswoman for the National Oceanic and Atmospheric Administration.

Humpback whales feed on menhaden, also known as bunker or pogies, and experts say that kind of fish is what likely drew the young whale into the inner harbor.

Although humpback whale sightings in Boston Harbor are uncommon, they do happen. The juvenile whale in the DCR video has been spotted several times in the inner harbor since Sunday. Prior to that, a group of five to six humpback whales were spotted in the outer harbor on Aug. 24 and 25, according to Laura Howes, director of research and education for Boston Harbor Cruises.

“Sometimes younger animals try different things,” she said.

Howes said the whales that venture into Boston Harbor are typically juveniles who are looking to feed.

“We’ve been seeing this on and off as recently as this morning,” she said Wednesday. “I’m guessing it may continue. It appears pretty healthy. As far as we can tell, there’s nothing wrong with it.”

The video of the whale breaching the water has been viewed thousands of times on social media.

“It’s exciting,” said Susan Kane, the islands district manager for the state Department Conservation and Recreation. “I know it’s not unheard of, but what’s different this time, they seem to be enjoying being here.”

Kane said it was fitting that the Deer Island waste water treatment plant was clearly visible in the video. After all, it wasn’t that long ago that Boston was known for having the dirtiest harbor in America. The presence of whales and other marine life shows just how far the harbor has come.

“It’s not a safe place to be. It’s an extremely busy harbor,” Howes said, worried about the whale’s safety. “It could easily be hit. We’re hoping it will go away, for its own safety.”

Vessel strikes are one of the biggest threats to humpback whales, according to NOAA, and they are also susceptible to getting tangled up in fishing gear.

Several boaters boarded by Reaser and his crew Wednesday were surprised to hear of the whale sightings.

“This makes me feel safer,” said Tonya Brooks, as Coast Guard officers made sure the boaters had fire extinguishes, life jackets, and a working horn.

Coast Guard Petty Officer Taylor Reaser shook hands with a boater as Petty Officer Jonathan McEneaney came aboard a boat for an inspection. David L. Ryan/Globe Staff

Ferreira said it’s important that mariners keep an eye out for whales and leave them alone. (For a complete list of NOAA’s whale watching guidelines, click here.)

“Don’t chase down the animals,” Ferreira said. “Just let them be.”

On the Coast Guard ship, Reaser passed a phone around the cabin to show the other crew members a video of the breach. Just a few feet off the boat, the whale’s head broke the surface, sending a spray of sea water high into the air.

“It’s amazing — it’s something different,” said Petty Officer Charles Damp, who has been with the Coast Guard for more than four years.

He’s seen whales and other large marine life out in the open seas near fisheries, but never in the harbor, he said.

“I’ve never even heard of that happening,” said Damp, scanning the surface hopefully as he wondered aloud if the great beasts were anywhere nearby.