It seems simple enough: an Internet site for real-time boat slip availability and booking. It’s the kind of idea that makes you wonder, why did I not think of that? Well, someone did. Portbooker.com, born in Palma de Mallorca in 2005, is positioning itself as the Expedia of the marine world. The easy-to-use site allows captain and crew to check availability in an expanding network of marinas around the world.

Although it probably could use a couple of refinements, the site is easy to use. Enter a city (you need the exact spelling), date of arrival and departure, boat length, beam and draft (in meters), type of yacht (motor, sail or catamaran) and hit search. Available marinas that meet the specified criteria and have online price and availability information come up with a green icon. Click on the marina listing to get an inclusive price for the stay you have specified, and you will also get marina information (location, services plus nearby hotels or car rentals).

If the price, location and criteria are suitable, click on “rent a mooring” and enter additional vessel information plus your contact and payment info (if you are a first-time user). You can also check other listed marinas that are not yet in the live booking system by entering your info and allowing Portbooker.com to do the legwork. If you are unsure of the spelling or what marinas are available in the area you are cruising, you can check marinas by geographical area (or other criteria) through the online nautical guide.

There will be naysayers. A European boatbuilder told us he did not think the system would work in high-demand areas with little berth availability where slips for large yachts particularly tend to involve cash transactions. Experienced captains may feel they can get a better deal or better service by picking up the Sat phone and negotiating a price directly with the marina of their choice, particularly if they are frequent visitors.

Did not Expedia or any of the other internet-booking sites face such objections at the onset? It does not seem to have stopped them from thriving, even if they have not captured the entire hotel booking business. Portbooker.com already seems to have overcome many of these objections. According to company executives, the site already has more than 17,000 registered users, information on 8,500 referenced marinas worldwide and a captains’ club, 5,000 strong. The owners of the site claim their 2011 bookings were up 19 percent over 2010.

Ancillary services include a blog under “community”, available to registered users and online boat rental (charter) services. Registered users can retrieve their bookings and data by signing on with their assigned passwords.

If you have booked hotel rooms online and this seems familiar to you, it is not accident. Robert Neuman, who is in charge of the North American operations, and Palma-based Jorge Velasco, both were hotel industry executives at some point in their careers.

To give it a try, see portbooker.com