I want to buy a gps/fishfinder for my boat, but what is a chartplotter? Do I need one to cruise offshore?

A GPS allows you to insert waypoints and give you time speed distance traveled and tells you where you are NOW. A chartplotter allows you to load charts so you'll have depths, currents, ports, etc, all of the "stuff" you have to go look at your rolled up chart for but still have to plot your position. The combo unit is VERY handy if you doing coastal cruising. When you combine the two, the chartplotter and the GPS, you'll know when you're about to run aground!! The GPS alone doesn't give you ocean charts. If I recall correctly the fishfinder will give you depth. They do make a single screen that displays all three. Make sure you get a color monitor.

A GPS is a Global Positioning System which will place you on the earth within 3 feet depending on the unit you have. From that fix you can transfer it to a chart and find out exactly where you are. A chart plotter is similar but has an LCD screen which will give a visual fix on the screen but you have to purchase the chips with it for the area you intend to travel in. My advice is to stick with a GPS and updated charts for offshore because when you get into the waterway you won't need either!!

listen to science teacher....... a chartplotter is a digital reproduction of a chart; the GPS puts a moving dot on the e-chart showing where you are........it's very good, but can fail for three reasons : gravity ( you drop it) water ( it gets wet) or electricity ( batteries die) Carry paper charts! Know how to plot your position.....the US Power Squadron or Coast Guard Auxiliary offers nearly free excellent courses on small boat handling out on the briny!