"Mom, they look like dead people," one of my daughters whispers.

It's 6 a.m. and my family is huddled on deck chairs in the pre-dawn chill aboard the Discovery Sun cruise ship. Other passengers sprawl around us under black rental beach towels, deep in slack-jawed sleep. The 20-something girl next to me is limp, her head resting on the arm of my chair.

But my two kids, ages 8 and 9, are too excited to close their eyes. As we glide away from Fort Lauderdale's Port Everglades at 8:30 a.m., our comatose neighbors stir, the sun warms our shoulders and the deck pool fills with water. The notion of swimming on a ship as it cuts through the ocean has thrilled my daughters since they saw pictures of the cruise on Discovery's Web site. They ignore a call for the day's first limbo contest and splash into the small, amoeba-shaped pool. The smell of fried food wafts across the deck.

Grand Bahama Island lies five hours ahead.

They're not billed specifically for families, but Discovery Cruise Line's round-trip sailings between Fort Lauderdale and Freeport are logical budget-minded getaways for people with kids. The "getting there" is part of the appeal. The day cruise is much cheaper than flying ($59.99 per adult, including three meals, compared to a round-trip airfare that starts at $227). Children, who cruise for free, are usually enthusiastic about exploring the ship, with its many decks, narrow hallways and staterooms, lounges and restaurants. A video arcade and kids zone help, too.

The other attraction, especially when it comes to families, is the scheduling flexibility. Passengers can come back the same day or stay several nights in a Bahamian hotel, taking advantage of one of eight Cruise 'N Stay packages offered through Discovery. Just catch the ship back on the pre-arranged afternoon of choice, almost like boarding a ferry.

"This was a quick, father-daughter trip for us," said Dragan Radulovic, a math professor at Florida Atlantic University in Boca Raton who was on the cruise as a day trip with daughter, Tatiana, 10.

The two explored the beach, swam in the infinity pool at the Westin Grand Bahama Our Lucaya Resort, and pecked around souvenir shops and stalls at the Port Lucaya Marketplace before boarding the ship back to Port Everglades at 3:30 p.m.

"We're doing a lot of bonding," he laughed.

Only those with stamina will want to do this in one day. Passengers are required to check in between 5:30 a.m. and 6:30 a.m. The ship doesn't return until 10 p.m., with another hour-long wait at the end to clear U.S. Customs. It's an "uber"-long day, especially for kids.

Those with toddlers might want to consider paying an additional $65 for a cabin as a quiet refuge for naps aboard the ship. That's what the Ferlita family from Jupiter did on our trip.

While sisters Taylor, 8, and Bailey, 7, competed in the hula hoop contest in the open-air Tropical Lounge and colored in the Club Discovery kids area below deck, their brother Noah, 3, snoozed for hours with Mom in the claustrophobic but useful stateroom.

As far as cruises go, this is a no-frills ship, with industrial carpeting, cafeteria-quality food and clean but weathered furnishings. The small, hole-like pool -- filled to the halfway point with seawater -- quickly lost its appeal after my girls sloshed around in it for a few minutes.

"It's decent. You get what you pay for," shrugged Lori Berger of Orange County, Calif., who was on the cruise as part of a Florida vacation with her husband, Keith, and two kids, Lahna, 5, and Kai, 2.

My husband and I opted for a two-night stay in Grand Bahama so we could truly relax. It gave us 2 1/2 days of playtime at the resort's pools and beach. The $690 it cost for our family of four covered the cruise, hotel stay and most harbor fees.

We spent our days poolside at the Sheraton Grand Bahama Our Lucaya Resort, where a winding slide kept the girls entertained for hours. The Sheraton, joined by walkways to the more upscale Westin, is part of a complex that includes restaurants, bars, shops, a children's center and several pools. Kayak rentals and a trampoline in the ocean drew us to the resort's white-sand beach, where a conch shack called Billy Joe's offered the freshest, tastiest cracked conch we've ever had. When we grew tired of sun soaking, we strolled across the street to poke around Port Lucaya's marketplace.

The resort's restaurants were pricey and predictable. Our best meal came the night we took the advice of a hotel worker manning a beach volleyball game and grabbed a cab to Simply Native, a no-frills locals restaurant with heaping plates of ribs and dirty rice with conch -- and prices no higher than the $10 entrees on the children's menus back at the resort.

Expensive dining aside, the trip's relative affordability appeals to a large variety of travelers, something that really became apparent on our return trip two days later. Ever wonder where the middle class is in South Florida, which seems to exist only for the very rich and very poor? We came together aboard this ship in all our glorious shapes and colors on that late Sunday afternoon.

There was the group of Muslim girls, some wearing black veils, listening to the Jamaican calypso singer. There were white grandmas in straw hats and sundresses clapping with middle-aged, suburban black couples as they cheered for contestants in the men's "knobby knees" contest. Guys in black T-shirts with Converse on their feet and mohawks on their heads bobbed with young backpackers in Birkenstocks to Bob Marley tunes on the loudspeaker. Middle-aged women with tube tops and tattoos mixed at the bar with balding men in socks and sandals, a few of them in wheelchairs.

Oh yes, and there were a handful of families like us.

The crazy-quilt quality of the crowd made for a strange mix of entertainment, ranging from bingo to beer-chugging contests. One minute my kids were competing with other children in a hula hoop challenge, the next a singer seeking audience participation was screaming, "Let's hear it for the sex maniacs!"

Three hours after boarding the ship to return to Florida, the top deck lounge started to feel like a Key West bar past midnight. We ducked below to the Starlight Showroom, where a jazz-and-blues singer and a magician kept the crowd subdued until we docked. We arrived at our Coconut Grove home close to midnight. As they faded off to sleep, my kids start to tick off all the trip details they planned to tell their friends in the morning. They were sunburned and slightly cranky, but they now considered themselves cruise authorities.

DISCOVERY DAY CRUISE: GRAND BAHAMA ISLAND

• Cost: $59.99 per adult roundtrip, including three meals (breakfast and lunch to the Bahamas, dinner on the way back to Fort Lauderdale). Children cruise free. Cruise 'N Stay packages are $100-$200 a night. My family of four spent a total of $690 for the cruise and a two-night hotel stay.

• What's on board: Casino, pool, video arcade, dance club, two lounges with entertainment, two dining rooms, gift shop, two bar-and-grills, staterooms, children's play zone, deck games and locker rooms.

• Additional costs: A $10 per person port fee must be paid in cash at Port Everglades; parking at the port is $15 a day; locker rentals on the ship are $5 each way to store carry-on baggage; cabins start at $65; beach towels on the ship rent for $1.50 each; snack food ranges from $2.25 for fries to $4.75 for chicken wings; a can of beer was $4.39 and mixed drinks were $5-$7; a cab ride from Freeport harbor to hotel cost $5 per person.

• Tipping: There's constant pressure on board to tip (there's even a tip cup in the kids zone); 15 percent tips are included in all bar and snack food tabs; tip suggestion cards sit on every dining table. We spent a total of $30 on tips round-trip.

• Travel details: Fort Lauderdale to Freeport service every day except Wednesdays. Passengers have to be at Port Everglades in Fort Lauderdale by 6:30 a.m. The ship arrives in Freeport about 1 p.m. On the return, guests are due at the ship by 4 p.m. It arrives back in Fort Lauderdale about 10 p.m., but passengers aren't usually cleared to disembark until 11 p.m.

• What to bring: Passports, sweatshirts (the morning deck air gets chilly), beach towels, plastic bag for wet swimsuits, sunscreen, dollar bills for tipping (the on-board ATM machine has an $8 service charge).

• Info: 800-259-1579; www.discoverycruiseline.com.

• What we liked: Flexibility of packages, friendly cruise staff, the novelty of swimming aboard a ship in the ocean, the water slide tower at the Sheraton Grand Bahama Our Lucaya Resort, white-sand beaches, fresh conch, the slow, laid-back attitude.

• What we didn't like: Getting up at 4 a.m. to catch the ship, the late-night return to Fort Lauderdale, a tip-badgering atmosphere on the ship, pricey food and no night activities at the resort, the hour-long waits in port before disembarking, the slow, laid-back attitude.

WHERE TO STAY

• Sheraton Grand Bahama Our Lucaya Resort, 242-373-1444; www.starwoodhotels.com. Part of a complex with a more upscale Westin, this is the best option for families because it has a sprawling pool and beach area, with a fun slide for kids, a casino, 11 restaurants, a children's camp, spa and shops. Rooms are small, but modern. Starting from $169.99.

• Pelican Bay at Lucaya, 242-373-9550 or 800-852-3702; www.pelicanbayhotel.com. Steps from Port Lucaya Marketplace and a 15-minute walk to the beach, the hotel has a West Indian gingerbread exterior, with rooms overlooking a pool and marina. Starting from $149.99.

• Port Lucaya Resort & Yacht Club, 242-373-6618 or 800-582-2921; www.portlucayaresort.com. An affordable option a short walk to the beach and next to the Port Lucaya Marina; has its own big pool, hot tub and restaurant. Starting from $90 plus $8 per person service charge.

WHAT TO DO

• Port Lucaya Marketplace, www.portlucayamarketplace.com. Souvenir and clothing shops and stalls, restaurants and bars in pastel colonial buildings on the waterfront.

• Snorkeling, kayaking, biking and eco-tours can be booked at the Port Lucaya Marina. A kid-friendly, two-hour Seaworld Explorer trip on a semi-submarine lets passengers view reef life from an underwater observatory and provides a snorkeling opportunity; $45 adult, $25 kids, ages 2-12.

• Dolphin Experience, 242-373-1244 or 800-992-3483 or 561-472-1100; www.unexso.com. Encounters with bottlenose dolphin, ranging from touching the mammals on a partially submerged dock to scuba diving with them on a reef; $75-$199 per person. Tickets available at the Underwater Explorers Society (UNEXSO) in Port Lucaya, but make reservations ahead of time.

WHERE TO EAT

The Sheraton resort's restaurants were expensive and disappointing. Venturing off property is worth the effort.

• Billy Joe's on the Beach, on the edge of the Sheraton Grand Bahama Our Lucaya Resort's beach, 242-373-1333. Freshly-made conch salad, cracked conch, grilled conch steak and fried conch, with fries and mixed drinks. $8-$10 a plate.

• Zorba's Greek Cuisine, at Port Lucaya Marketplace, 242-373-6137. The best breakfast we had, with hearty pancakes, eggs, bacon, sausage, toast and home fries. $5-8 breakfast entrees.

• Simply Native Outback Restaurant, on East Beach Drive, just off East Sunrise Boulevard, Lucaya, 242-352-5003. No menu, no-frills local hangout with delicious barbecued ribs, baked lamb, and fresh conch and fish when available. Recommended by a hotel staffer and worth the cab ride. $10 entrees.