One of the most complete photo collections of Monterey Bay marine animals in existence can be found on the bookshelves of a tidy retirement condo in Pacific Grove.

Thousands of slides of starfish and anemones, sea slugs and kelp bladders fill binder after binder in the office. Stunning shots of strangely textured tentacles, delicate spines and translucent bodies of the bay's many miniscule inhabitants decorate the walls.

The images are the hard-won result of 25 years of underwater photography by Lovell and Libby Langstroth, scuba divers and amateur marine biologists extraordinaire.

Marine photography is a second career of sorts for both, as they didn't start diving until they were in their 50s. A book of their work, "A Living Bay: The Underwater World of Monterey Bay" is being published by UC Press in October.

Lovell, a physician, was thefirst to start diving. He had always been an avid backpacker, skier and river rafter, and jumped at the chance to explore a new universe in the 1960s.

"At the time, recreational diving was just opening up, and equipment was just becoming available to take underwater pictures," Lovell said.

But Libby had the earlier association with diving. On her desk she keeps a picture of herself at age 14 holding a bicycle pump connected to an old-fashioned diving helmet on her brother's head. She used to supply him with air as he dove in the Berkeley Marina.

Libby and Lovell married in 1975, while she was halfway through her scuba certification class. Their busy professional schedules gave them time to dive only on occasional weekends until they retired to the Monterey Peninsula from Berkeley in 1980.

"When we first came, we got involved in auditing courses at Hopkins Marine Station and Moss Landing Marine Laboratories. We were always interested in the funny things we were seeing," Libby said. "We would learn about these creatures, go diving to hunt for them and try to photograph them."

Probably the most exhausting, but also the most useful, of these courses was a Hopkins class on subtidal ecology. "The class had 30 students:28 Stanford undergraduates and the two of us old folks. We dove every day for five weeks, had two hours of lecture a day and lab every day," Lovell said. With the class, they explored virtually every dive site on the Monterey Bay down to Big Sur

They grew so dedicated to capturing marine animals on film that they often went to great lengths to ensure a photo. Once they came across a sea slug they had been searching for at Point Lobos, but then realized their cameras were out of film. "We ran home, changed the film and got back in time to get the picture," Libby said. No small feat when getting in and out of the water requires fumbling with heavy layers of neoprene, cumbersome weight belts and steel air tanks.

They soon began taking some of the creatures home for a few days for underwater studio sessions, eventually becoming experts at bringing out the details of animals as tiny as 1 milllimeter with their 14x enlarging lens setup.

"This has been great for us, working together, learning together and exploring together," Libby said.

Over the years, the couple has logged more than 650 dives off the Monterey Peninsula, and that's not even counting the vacation dives they've taken in the Caribbean, New Guinea, Palau, Micronesia and the Philippines.

"Luckily, we didn't get into more trouble than we did," Libby laughs. "Once we came up and the inflatable had floated away. We were too tired to swim that far so we dumped our tanks and weight belts and snorkeled back." They were able to retreive their gear the next day.

Word of the Langstroths' growing phhoto collection spread through the local marine biology community. The pair began giving slide shows and lectures, including one with the racy title "Sex in the Kelp Bed." Articles in major magazines and an exhibit at the Canadian Museum of Nature in Ottawa spread t heir fame further.

So when curators were preparing the Monterey Bay Aquarium for its grand opening in 1984, they turned to the Langstroths for graphics still being used in about 50 of the educational displays.

When a local publisher suggested they present their fantastic photo collection in a book, both jumped at the chance. By 1997 the couple had ssent the first two chapters to UC Press, which promptly offered them a contract.

"That was the miracle of the ages," Lovell said.

The book's selection of subjects is "idiosyncratic--we put in what we think is interesting" Libby said. Themes include the multistep life cycles of many tiny sea creatures, and aspects of animals that reflect issues in human biology such as tissue rejection.

Assembling the photographs was relatively simple, but composing the text was another matter entirely. Lovell said they once passed along a rough draft to a review who "said it read like we were writing for the Blue Book," he laughed. After a bit of editing help from local marine biologists and other friends, the crowning achievement of their underwater adventures went into production earlier this year.

The Langstroths finally quit diving four years ago when Libby turned 75 and Lovell turned 80, but they still tidepool and bring home the occasional specimen to study under the dissecting microscope in their kitchen.

"A Living Bay: The Underwater World of Monterey Bay" by Lovell and Libby Langstroth will be available Oct. 2 from UC Press. The cost is $60 hardcover, $29.95 paper.

--Kathleen M. Wong