Late summer is the Gulf of Mexico's peak offshore fishing season. Migrant game fish species move in Texas waters this time of year and, barring tropical storms or hurricanes, the late summer weather is predictably calm.

Calm weather is a key factor for all but the most experienced, diehard offshore anglers. Offshore fishing requires long boat runs that become uncomfortably rough when the wind blows. Once on the fishing grounds, heavy seas make fishing difficult at best, miserable at worst.

The attraction for deep-sea anglers is threefold. Offshore is where the big fish roam, so you never know when a bait intended for a 10-pound red snapper might tempt a much bigger denizen. There are pelagic fish that eat 10-pound snappers, and offshore veterans usually have a tale or two about encountering giant marlin or sharks. The tales are usually about the big one that got away. It takes specialized fishing equipment and a considerable ration of pure luck to handle offshore giants.

For most casual freshwater anglers, a 20-pound fish of any species represents a personal best catch, and 20-pounders are common in the deep blue sea. The variety of species encountered on an offshore fishing trip is another attraction. Common offshore fish fights in the 20-pound weight class occur with amberjacks, king mackerel, cobia, an assortment of shark species, tuna, wahoo and barracuda.

Even when the fishing is slow around offshore structure, you can almost always rely on triggerfish, bluefish, bonito, Spanish mackerel, blue runners, pompano, dorado or grouper to provide action.

Finally, fishing beyond sight of land spells an undeniable adventure to the average landlubber. The Gulf of Mexico's deep blue offshore waters are much different than the murkier inshore waters. The ocean's essential mystery hasn't changed much since Columbus set sail. You might see a whale shark, a giant manta ray, a school of frolicking porpoises or a five-acre shoal of bait fish being hammered by hundreds of predatory fish.

Here are five things to consider if you're planning an offshore fishing trip:

■ Offshore fishing is expensive because it requires a large, seaworthy boat and a lot of fuel. Offshore trips from Texas ports often target structures 40 miles or further from the dock. From tackle to bait to the amount of ice required to preserve the catch, everything about offshore fishing is expensive.

■ If you don't own an offshore boat or know someone who does, there are basically two options. The least expensive method of offshore fishing is from a large vessel typically referred to as a "party boat." Party boats are a bargain because the expense is shared by 30 to 80 anglers. Prices range from $60 to $100 for a fishing trip that lasts six to 10 hours. Longer trips are offered at higher prices.

Overnight trips that last as long as 36 hours cost as much as $350, but the number of anglers aboard for an extended trip is usually restricted, and the overnight trips offer the best potential for fishing success. The downside of a party boat experience is the crowd. You could be assigned to fish from a numbered spot on the rail and, on a crowded trip, have no latitude to change your fishing spot.

The second, and more expensive option, is to charter an offshore boat. The charter fee may range from $1,000 to $2,500 a day, depending on the size of the boat and amenities provided. That cost may be split among as many as six anglers, again depending on the size of the boat. The advantage of a charter is that the captain works for you and should fine-tune fishing strategies to suit his clients.

■ Fishermen who have problems with motion sickness tend to avoid offshore fishing. Great strides have been made in motion sickness medications, however. Before traveling to the coast, ask your doctor about a prescription for scopolamine.

■ Offshore fishing requires specialized tackle, and most party boats and charter boats furnish tackle and bait. If you plan to bring your own tackle, clear it first with the charter service. Light tackle offshore fishing can be great fun, but it's best done from a chartered boat shared with good friends.

■ Follow expert advice. Whether it's the party boat deck hand or a charter boat captain, old salts know the best techniques for successful offshore fishing.

Galveston: Galveston Party Boats, Inc., www.galvestonpartyboatsinc.com; 409-763-5423.

Galveston: Williams Party Boats, Inc., www.galvestonfishingboats.com; 409-762-8808.

Port Aransas: Fisherman's Wharf, www.wharfcat.com; 1-800-605-5448.

Aransas Pass: Offshore Adventures Deep Sea Fishing, www.portaransasadventures.com; 1-800-567-5132.

South Padre Island: Osprey Fishing Trips, www.ospreyfishingtrips.com; 1-888-867-7739.