SARAH JONES’S first real sense of what it might be like to be a marine biologist came during summers at Seacamp San Diego, a camp for middle-school and high-school students. It was there that her curiosity about the field evolved into an academic and career choice.

Ms. Jones, 25, is about to begin a Ph.D. program in biological oceanography at the Florida Institute of Technology in Melbourne. She wants to become a marine biology professor and to conduct research into seahorse conservation and preservation.

The type of camp that inspired Ms. Jones as a teenager is gaining popularity, and is part of a larger trend toward environmental and science camps. About 50 camps, most of them near the ocean, now specialize in marine biology studies, according to the American Camp Association. That is an increase of about 25 percent since 1998.

“Kids today want to tackle problems and be part of the solution,” said Peg Smith, executive director of the American Camp Association. “They want to actually be exploring tide pools and working in aquariums. They want to be experientially involved.” At the same time, demand for biological scientists is growing, according to the Bureau of Labor Statistics.

Seacamp San Diego offers year-round marine biology programs; during the winter, the offerings are geared toward science classes from around the country. In the summer, campers from 12 to 17 years old come for its one- and two-week programs. Seacamp I is designed for beginners and costs $775 for a week.

“We play a game with the younger kids to teach them how to classify groups of animal arthropods,” said Amy Bergen, the camp’s assistant director. “We blindfold them and put live animals in their hands: sea stars, sea urchins, crabs, lobsters and big slugs. There’s usually a lot of screaming, but the kids get really excited.”

The Seacamp I participants are introduced to the labs, where they dissect squid and mackerel, learn about invertebrates like snails and starfish and study marine mammals like dolphins and whales. (Ms. Bergen refers to these resident superstars as the “charismatic megavertebrates.”)

Seacamps II and III are for older children and include deep-sea scuba diving, lectures about sustainable fisheries and conversations with research scientists. Camp II costs $1,150 for a week; campers can choose to stay for a second week for a total of $1,925. Camp III costs $1,375 for eight days; only high school students can attend.

Many of those who attend Seacamp return annually, progressing to three-week internships or full-time summer counselor jobs. That was the case for Jennie Gowan, 20, now a senior at the University of California, Santa Barbara, who is majoring in evolution and ecology, with an emphasis in marine biology.

Ms. Gowan, a San Diego native, spent parts of nine summers at sea camp and decided by the age of 14 that she wanted to go into marine biology. An avid scuba diver, she is spending this summer on Moorea, one of the Polynesian islands, as part of an ecological research team. She receives a $2,500 stipend for her research assistance.

Ms. Gowan credits her years at Seacamp for her fascination with the field and with scuba diving. In fact, many campers say that diving gets them hooked on marine sciences.

Shannon O’Neill, 20, who will be attending San Diego Mesa College in the fall as a marine biology major, first started diving in the flooded quarries of Ohio, her home state.

She discovered that by attending Seacamp in San Diego, she could pursue her passion for diving in the Pacific Ocean while surrounded by dolphins and starfish — instead of the sunken automobiles often found in Midwestern quarries.

Diving is what attracts many campers to the Catalina Sea Camp, on Catalina Island off the Southern California coast. Scuba divers and snorkelers at the camp shoot their own underwater film — often getting footage of sharks and sea lions. The camp offers two three-week sessions for boys and girls ages 12 to 17. The cost is $3,100.

While the program at Catalina is oriented toward marine biology, it is not as academically focused as the camp in San Diego. At Catalina, the two favorite classes, seafood cookery and surfing, are only peripherally related to marine biology.

“Our main focus is not just academic, it’s social,” said Paul Kupferman, the summer camp director at Catalina Sea Camp.

Still, there is plenty of hands-on experience. In addition to the diving activities, the camp has a lab with a shark-touching tank, and campers set up and care for their own aquariums in the camp’s dormitories.

Setting up aquariums at home is another popular hobby of sea camp veterans. Ms. Jones, the Florida graduate student, spent a semester working as an aquarist at the Shedd Aquarium in Chicago and set up a small goldfish tank while she was still in high school. She later traded up to a 10-gallon and then a 45-gallon freshwater tank.

Perhaps the most commercial and spectacular sea aquariums available to campers are those at the SeaWorld parks in San Antonio, Orlando and San Diego. SeaWorld is host for adventure and career camps for grade schoolers to college students, offered year-round.

Allison Lipsay, 15, of Great Neck, N.Y., will be attending the career camp at SeaWorld San Antonio later this summer. The camp costs $950, and she will divide her time among the aquarium and the animal training and animal care departments.

She is considering a career in marine biology or veterinary medicine and will have an opportunity to prepare diets for whales, sharks and dolphins.

While sea camps offer a chance to explore the possibilities of a career in marine biology, they may also be the place where campers decide not to move in that direction.

“You learn later on that real marine biology is about physics and chemistry and math, not necessarily about diving and dolphins and whales,” Ms. Jones said.

“But it’s a good eye-opener even if you don’t go into the career,” she said. “It helps you gain a respect for nature and a sense of what’s going on with the environment.”