@Kingdw Thanks for reaching out!
Depending on the level of detail you are looking for, @Philreedshikes advice may be just what you're looking for. In terms of handheld units, we have a couple of models of GPS units that can be used for both hiking and marine use. Take a look at these models:
Both of those units will take an SD card, which can be loaded with Garmin's Marine map software or with a Garmin Map. We also encourage you to check out this conversation, Advice for a GPS for hiking and kayaking, which may have some useful insight as well.
Additionally, if you'd like more good info on GPS units, check out the expert advice article, How to Choose and Use a GPS.
Hopefully this helps!