The Hydrografx maps are for use on a computer. You can then enter waypoints into a GPS to find the spots you are interested in. Any handheld or boat GPS will work.
Thanks. I'm not too computer savvy, but I understood that the Hydrografx maps are used on a computer. I was just looking for suggestions about GPS brands and models. I guess that I would just need to make sure that the GPS unit that I bought would accept a SD card?