The most popular brands of GPS systems include Magellan and Garmin. Both offer marine GPS and are available on sites such as Amazon and in stores as well.
Depending on the brand and model, the number of points one can plot on a GPS varies. For marine use, a chartplotter GPS with a fishfinder is recommended.
A good place to shop for a marine GPS is Calibex. There is a large variety to pick from and the prices range from $129.99 to $499.95. Best Buy is also a good store to purchase a marine GPS.
You can find the difference between marine gps systems and garmin gps systems on the following site: http://www.secrets2business.com/the-difference-between-marine-gps-handhelds-and-their-bigger-brothers/. They have good descriptions.
There are many good places one can look to purchase a Garmin Marine GPS. Some good places include 'Best Buy', 'Amazon', 'eBay' and from 'The GPS Store'.
The Magellan Marine GPS is fairly priced at $105.36 (new) and $104.16 (used) through Amazon.com http://www.amazon.com/Magellan-Meridian-Marine-Waterproof-Hiking/dp/B00005OLY9
A good use for a marine GPS Plotter would be if you took it fishing with you on your boat. It will help you keep track of your location and will ensure that you won't get lost.
You can find a used Marine GPS on ebay or craigslist. Amazon is a good place to find a GPS too, because the site is secure and you can be sure that your money is going where you think it is.
The Garmin Forerunner 405 GPS are an accurate brand of GPS and a good watch.
There are many retailers that offer marine GPS products, and it is very easy to locate them on Amazon, Ebay and BestBuy. However I would recommend purchasing one from a specialized retailer such as WestMarine as they can offer valuable advice according to what marine GPS would be the best choice for your husband's little boat.
The the Garmin GPS 72 is a waterproof marine GPS unit.
Magellan is an excellent brand of GPS for the prices offered. Especially if this is your first purchase of a GPS system. It works very well for avoiding traffic.
Gramin Gps is a very good brand. It is number one in the industry of GPS. The company has been in business since the late 1980's. They have been selling millions since and always have the latest technology.