Whale Cay, a nondescript mass of rock that juts up out of the Windex-blue waters of the Sea of Abaco in the Bahamas, offers no significance other than its location. The little island lies dead center in a crucial passage between the peaceful, protected waters in the northern Abacos, where Walker's Cay is located, and the equally-placid southern Abacos, where you'll find Marsh Harbor, the island group's biggest town.

Because the Sea of Abaco, the big, azure bay that is one of the Bahamas' best cruising grounds, gets incredibly shallow to the west and south of Whale Cay, mariners with anything that draws more water than a jet boat are obliged to venture out into the ink-blue Atlantic, to the north and east of Whale. It's the only way to travel between the two halves of the bay. Many boaters who haven't been to the Abacos before find out about the Whale Cay shallows the hard way, losing a prop in the process. No signs or channel markers warn you of the shallows, even though they present the toughest obstacle to navigation in the Abacos.

Those new visitors savvy enough to realize they have to go around Whale Cay on the open ocean side often get into even bigger trouble because they don't know about the strong tidal surges that can dash your boat on the tiny island's rocks before you know what hit you. The rocks on Whale Cay's ocean side are often littered with chunks of broken boat hulls, and more than one boater has died there over the years.

But the first time I traversed the Whale Cay passage, it was easy. I left the little island a good 300 yards off my starboard beam, then easily slipped around the coral reefs that lie just below the surface of the water just south of the island, and was back in the calm, clear waters of the bay in a matter of minutes. Even though I'd never been to the Abacos before, I made the Whale Cay passage like an old pro for a simple reason: guidebooks. A couple of weeks before I went to the Bahamas on that trip, I bought not one but four guidebooks with information about the fine points of cruising the Abacos, including how to handle Whale Cay ... and live to remember it.

Any experienced boater will tell you that when it comes to navigating dangerous waters, there's no substitute for local knowledge. Fortunately, local knowledge is something you can acquire quite easily, with an armload of marine guidebooks.

The best thing a guidebook can do is save your life. But they can also make the quality of life on your cruise a lot better. Guidebooks can help you find marinas, boat repair yards, marine supply stores, hotels, restaurants, clubs and bistros near the water — just about any amenity you want.

Guidebooks, which can be found in most any marine store or marina ship's store and in many larger bookstores, aren't usually cheap. Expect to pay $35 to $40 for a good one. But they're the next best thing to having a local guide on board for your cruise, which would cost a lot more. Because guidebooks are available for almost any popular cruising area — you can even get them for overseas spots like the Greek islands and the coast of Turkey. I always make guidebook research the first step when I am planning a cruise. Once I get to the cruising area, I also check out the local marina's ship stores, because they are often the source of guidebooks that can only be found in the local area.

I never settle for just one guidebook. You can usually find overlapping layers of guides. My trip to the Abacos offers a good example. I used the venerable Southern Waterway Guide, published by Intertec Publishing, which covers the entire East Coast, plus Bermuda and the Bahamas. I also used the Yachtsman's Guide to the Bahamas, which covers all of the Bahamas, with more detail than the Southern Waterway Guide. And I also used the Cruising Guide to Abaco, which only covers the Abacos and offers details you want find in the Yachtsman's Guide.

I also carried another important reference volume, Reed's Nautical Almanac, North American East Coast edition, which offers important info that won't always be in the guidebooks: tide tables and the exact GPS position of known aids to navigation in the area, like numbered channel markers and lights. With a Reed's and a GPS, it's frequently easy to find out where you are in relation to where you want to be. Those tide tables can be vital when you are trying to calculate, for instance, when to run through an inlet that goes dry at low tide.

Because I have taken quite a few cruises on boats I chartered in different areas over the years, I've amassed quite a personal guidebook library. Here are some of my favorites:

The Southern Waterway Guide (also available, the Mid-Atlantic Waterway Guide and the Northern Waterway Guide) by Intertec Publishing of Atlanta. Updated every year since its founding in 1947, this guide offers a wide range of information including tables that list the goods and services offered at local marinas, along with the telephone numbers of those marinas. (It gives you a good chance to call ahead long before you take your trip.) The guide also offers narrative sections about how to make various passages and approaches to harbors and inlets along the way, as well as a listing of what NOAA charts you'll need for a specific section of your travels. The weaknesses of the guides are that they cover such a large area that they can't give you a lot of detail about each area, and that the small charts reproduced the pages are often nearly impossible to comprehend. (The guide itself suggests you always carry the full-sized NOAA charts.) This is the guide that a lot of people used to call the "Walter Cronkite Guide," because his photo was on the cover for years, although it's not on the 1998 edition. Suggested retail price: $36.95

Embassy's Coastal Cruising Guide to the Atlantic Coast. Billing itself as the first cruising guide to cover the entire east coast (because the Intertec books split the coast into three volumes) this eye-appealing book offers lots of color photos and charts, as well as useful articles about where to go scuba diving and fishing along the coast. Dozens of color ads for marinas, in a standardized format that includes a small chart showing how to approach. Other charts in the book however, are disappointments, with no water depths or navigation aids. Suggested retail: $19.95

Intracoastal Waterway Facilities Guide (Paradox Publishing, Ludlow, Massachusetts. This guide covers 3,400 miles, from Boston to Tarpon Springs, Florida, but it's essentially just a compilation of full-page marina listings, with minimal narrative covering the waterway itself. The price is right, however. Suggested retail: $12.95.

Yachtsman's Guide to the Bahamas (Tropical Isle Publishers, Inc. Miami. The best overall guide to the Bahamas, the Yachtsman's features both hand-drawn nautical charts and some unique drawings that show what the approaches to various harbors and marinas look like from the sea-level view. By reading the narrative about the various destinations, you can find out all kinds of great tidbits about marinas, restaurants, stores where you can buy provisions, and more. However, phone numbers for the businesses are not listed in the text, and there are no tables of goods and services providers like you'll find in the Intertec guides. Suggested retail: $25.95.

Southeast Guide to Saltwater Fishing & Boating (International Marine, a division McGraw Hill. Illustrations and text about every salt water fish you can find in the region, plus detailed charts on the best places to catch them. Basic marina listings, with phone numbers and locations, but no details about services offered. No color illustrations inside the book. Suggested retail: $24.95.

Chesapeake Bay Cruising Guide (Wescott Cove Publishing Co. Stamford, Connecticut. With more than 400 pages of text in each of the two-volumes used to cover the Chesapeake (upper bay and lower bay), this well-researched guide offers lots of nice detail about one of North America's most popular cruising grounds, as well as the rivers and creeks that feed into it. Includes hand-drawn maps of popular waterfronts like Baltimore and Annapolis, with locations of various shops and restaurants you might enjoy. Lots of good charts, with numbered legends to point out locations of good spots to sight-see, fish or go ashore and visit a museum. Even though this guide is pricey ($39.95 per volume) it contains no color illustrations inside. (Wescott also publishes a good variety of foreign cruise guides, including places like Turkey, Tahiti, Guatemala and the Windward Islands.

Quimby's Crusing Guide, published by The Waterways Journal, Inc. St. Louis. This ambitious, 200-page guide covers more than a dozen rivers, including the Mississippi, the Ohio, the Allegheny and the Tennessee-Tombigee Waterway, so there isn't enough room for loads of detail. There is, however, a good listing of marinas and other facilities, complete with mile-marker locations and telephone numbers for those who, like me, consider a cell phone a must piece of equipment on any cruise.

This list of guidebooks only covers a fraction of what's out there. Spend a few minutes on the phone calling the area where you plan to cruise, and you can probably acquire three or four competing guidebooks for any area you can name. As far as I am concerned, that's the most important first step in planning any cruise. To me, a good guidebook is as important as a good boat.