As they plan their trips, folks who vacation at sea sometimes bob from ship to ship, cruise line to cruise line. They may be drawn by price, a quest to sample different styles of food and service, or the tease of hot new vessels.

Many cruisers, however, find a comfort zone on one or two lines and return, year after year, often to a familiar ship, sometimes to the same cabin.

For their passenger loyalty, cruise lines pass out rewards. These are not nearly as lucrative nor as husbanded as frequent flyer mileage. But they can improve your voyage with such perks as free Internet time and onboard discounts.

Current wisdom among frequent cruisers — from conversations and Internet forum sites — is that most people would not switch cruise lines because of loyalty perks. They see them more as added benefits than enticements to choose a particular cruise company.

Passengers are enrolled automatically into most loyalty programs after one cruise.

Cruise lines will enhance the goodies as the number of your vacation voyages increases. Think discounts on future cruises (typically 5-10 percent), private cocktail parties, complimentary Internet minutes, casino vouchers, logo souvenirs, cabin upgrades, shipboard credits in the shops and spa, priority check-in at the cruise terminal, and free laundry.

If you’re looking for a free cruise, don’t start thinking about tomorrow. For that ultimate loyalty prize, you may need to spend more than a year at sea to qualify. For instance, if you cruise 25 times on Carnival ships, you get 25 percent off your next cruise fare. Sail 50 times and get 50 percent, 75 times and get 75 percent off. After 100 cruises, your next cruise is free – which could mean nearly two years of cruising for a free week at sea.

Each line has its own version and program to reward loyalty — among them, Latitudes (Norwegian), Crown & Anchor (Royal Caribbean), Captain’s Club (Celebrity), Oceania (Oceania), Captain’s Circle (Princess), Mariner Society (Holland America), World Club (Cunard) and Very Important Fun Person (new and unusual from Carnival, which calls it VIFP).

Most lines tout their own loyalty program as among the best, because they want your business. After all, the vacation client easiest to find is the one they already know. And, as most cruise passengers say they return home pleased by their vacation, cruise lines know that the client easiest to satisfy is the one who already likes them.

What follows are examples of perks you can expect as a loyal cruise customer. These programs change occasionally (most are detailed on cruise line websites). As a member, you will hear from the cruise lines by email to tout their latest offers, itineraries, and discounts that sometimes are not the lowest price in the market. A reliable travel agent who specializes in cruises may have information about a better deal or lower price.

Royal Caribbean, for instance, uses a point system. Passengers get one cruise point for every night aboard ship, double points in a suite. After your first cruise, other trips include a cocktail party. Book a future cruise while onboard to get a bonus of up to $200. You get an amenity pack, with beverage, after 55 points, a daily breakfast with specialty coffees after 80, use of a concierge lounge after 175. Best perks, free cruise days and upgrades go to members who amass 700 points and are known as Pinnacle.