Agaptimoss, a 6-month old harbor seal, is wearing a satellite tracking tag that will help veterinarians monitor how well he does in the wild. Photo: Alex Washburn/WIRED Harbor seals Agaptimoss (left), Lira (center), and Ranger Luke (right) in their pool at The Marine Mammal Center. Photo: Alex Washburn/WIRED Veterinarian Greg Frankfurter makes sure everything is ready for the pre-release examinations. Photo: Ariel Zambelich/WIRED The teams draws some blood from Agaptimoss during his pre-release examination. They want to make sure all looks normal before letting him go. Photo: Ariel Zambelich/WIRED The team sticks the satellite tag on Agaptimoss. They're using a form of waterproof superglue that sets in a few minutes. Photo: Ariel Zambelich/WIRED Agaptimoss gets his sat tag. Photo: Ariel Zambelich/WIRED Veterinarian Greg Frankfurter (back) and volunteer Doug Hailey (front) check Agaptimoss's satellite tag and put on a flipper tag. Photo: Alex Washburn/WIRED Agaptimoss waiting for transport to the beach in Monterey. Photo: Alex Washburn/WIRED The seals are transported in dog crates. Photo: Alex Washburn/WIRED Doug Hailey waters down the seals during the nearly 3-hour drive from Sausalito to Monterey. Photo: Alex Washburn/WIRED Agaptimoss on the final stretch to the beach. Photo: Alex Washburn/WIRED Volunteers carried the seals to a private beach in Monterey. After a bit of hesitation, Agaptimoss (center) and his harbor seal friends headed straight for the water. Photo: Alex Washburn/WIRED Lira made it to the water first, followed by Agaptimoss and Ranger Luke tied for second. Photos: Alex Washburn/WIRED Hunney, a 7-month-old elephant seal, also got to go home on Thursday. She'd been at The Marine Mammal Center since the beginning of August, being treated for malnutrition and parasites. Photo: Alex Washburn/WIRED A last look toward the shore, and then the seals joined their friends. Photo: Alex Washburn/WIRED

Four small seals are crossing the Golden Gate Bridge, safely strapped into the truck in front of us. Tucked inside their crates, the quartet – three harbor seals and an elephant seal – are on a journey back to their ocean home. The destination: a beautiful, protected cove in Monterey Bay, bordered by a private beach.

Seals crossing the Golden Gate Bridge. Photo: Alex Washburn/WIRED

For the last few months, the seals have been at The Marine Mammal Center in the Marin headlands, where rescued marine mammals go to recuperate from injuries and illness. Responsible for 600 miles of California coastline, the center normally treats around 600 animals per year. This year, though, the mass sea lion stranding in southern California meant the facility helped overwhelmed rescue centers by taking in an additional 67 animals from down south. In a normal year, the center treats between 60 and 130 harbor seals; this year has been slow, with only 49 so far, and a really high success rate.

We pass the San Andreas fault running to the west of I-280, zoom through the concrete wilderness of Silicon Valley, and zip by the artichoke fields near Castroville before turning toward the southern Monterey Bay sand dunes, and the ocean beyond. It’s the farthest inland these seals will ever be.

WIRED will be tracking the journey back into the wild of one of the harbor seals, named Agaptimoss, a 6-month-old harbor seal rescued in June from a beach between Aptos and Moss Landing (the origins of his name). Malnourished and partially blinded by cataracts and retinal degeneration, he was brought to the rescue center for rehabilitation.

After an examination, an ophthalmologist determined the cataracts in Agaptimoss’ right eye did not seem to be worsening, and that he could still partially see with it. Now weighing around 50 pounds, the young harbor seal has gained enough weight to be released and has passed his “live fish test,” proving that he’s capable of catching food, said veterinarian Rebecca Greene.

The satellite tag Agaptimoss will wear. It's made by Wildlife Computers and talks to several satellites. Photo: Ariel Zambelich/WIRED

His vets are hoping that good vision in one eye will be enough for him to survive and catch fish. But they're not content to just wonder about his fate. Last week, the team attached a satellite tracking tag to his head, using a waterproof superglue. The tag uses as many as seven satellites to pinpoint its position; it’ll relay that information back to The Marine Mammal Center multiple times a day until the signal quits. “We won’t know if it's tag failure, or if it fell off, or if the animal died,” said Lauren Rust, who will be collecting the location data for the center.

Location accuracy depends on how many satellites the tag can find, and uncertainties can vary from between a few hundred meters to as many as 2,500 meters, Rust said.

If it looks like Agaptimoss is having a hard time – spending too much time hauled out on land, for example – the team has a plan. “If it appears he is not thriving well in the wild, we will use the satellite information to locate him and bring him back into rehabilitation,” said veterinarian Shawn Johnson. “At that time, we will determine if he is a good candidate for permanent placement in a zoo or aquarium.”

You'll be able to follow Agaptimoss along with us as we map his locations on our Map Lab blog.

Agaptimoss’s other traveling companions are Ranger Luke and Lira, also 6-month-old harbor seals, and Hunney, a 7-month-old elephant seal. They all have flipper tags, and Lira and Hunney are wearing numbered hats. Those accoutrements – as well as the satellite tag – will stay on until the glue fails or the seal molts.

On September 5, as the center's staff prepared the quartet for the trip home, I asked veterinarian Greg Frankfurter how he felt about sending them off. “I’m happy to see them go – it’s my job to get them back out there,” he said. Then he asked me to wave goodbye to them, from the beach. Which I did.

Near Cypress Point, along 17-Mile Drive, a crowd had gathered to watch the animals return home. As the harbor seals’ crate doors opened, three little heads peered cautiously out. Lira charged down the beach first, followed by Ranger Luke and Agaptimoss tied for second.

The trio dove into the gentle waves. After a few splashes, three heads popped up a few meters out and looked back toward the volunteers and staffers on the shore; then they headed farther out, where a welcoming party of harbor seals waited in the kelp.

Once, Agaptimoss came back to the beach – and then he was gone.

“When we release sea lions, sometimes they go up to each other and touch noses,” said Doug Hailey, touching the tips of his index fingers together. “And then they go their separate ways.”

Hailey has been volunteering with of The Marine Mammal Center for more than a decade, and, with volunteer Stan Jensen, helped oversee this trip home.

It's a big ocean out there, especially if you're a 50-pound seal. I wondered whether Agaptimoss would miss the fish-mash and bright blue pools at the rescue center. Where will he go? Visit Map Lab to find out.