Bests & Worsts Reviews from Amazon

I got my Garmin 78sc in 2010, to use not only on the water (Chesapeake Bay), but for hiking and geocaching. By now (2010) I've sailed for 3 days,(about 15 hours total run-time), and the alkaline batteries are about half gone according to the meter, so I'm fairly satisfied with the battery life. I haven't tried NiMH rechargeables yet. I was concerned the unit was going to be huge (it's intentionally large to give internal air space for water flotation ability), but it's not too big or heavy. It was smaller than I was expecting it to be. Also, having the buttons on top of the screen are a little weird, but it's not a big issue in use. It's very fast in finding the satellites and switching display screens, etc. The built in electronic compass (multi-axis)calibrates quickly, and reacts quickly to movement, but seems very accurate. There is an option to have the map orient to either the compass heading (direction you point the GPS) or from the track (direction you were moving in is oriented "up"). This is my third hand held GPS--before this I had a high end Magellan and a DeLorme with topo maps. I am much more impressed with this unit than the others. Of course, technology marches on, but the famed "ease of use" that Garmin GPS's are known for, along with the raw capabilities of this unit for marine use are there along with the faster speed. There's even greater functionality buried in the menus, so keep exploring if you don't see what you need. So far, I'm very happy. It has all the marine functions I was hoping for. The included g2 coastal marine charts are good, very readable in bright sunlight. It has a "Man Overboard Button" where when pressed and held, not only marks the position, but immediately give you the option to navigate back to that position. It also has "Anchor Drag" alarms, as well as low water depth and high water depth alarms (that key off the chart depth readings from low tide). All these alarms are adjustable by the user. I bought a separate Garmin boat mount made for this unit. I have not mounted it on the boat (3 screw holes required), but it seems to hold the unit well, with some adjustability for viewing angle. Like all handheld Garmins, the "basemaps" on the 78sc (on land, not on the water)are fairly useless, and optional maps can be expensive. Keep in mind that on the 78SC, the coastal marine charts are included (and very good and look like the raster NOAA charts). I recently loaded the separately purchased TOPO 100K US maps on DVD. When I loaded as many map regions up to the 78sc's internal memory (1.6GB I think?), about 70% of the continental US would fit, and it took a few hours to convert and upload via USB. I did not try loading up more maps to a separate MicroSD card. I have not used the topo maps yet, or the Geocaching functions of the Garmin unit, but they seem impressive looking at the menu options. Like I said, so far I'm very impressed, and looking forward to learning all the other capabilities of the unit, as well as checking out the Topo maps and Geocaching functions. UPDATE NOV 2013. Ok, now I've used the GPSMAP 78sc for almost 3 seasons sailing in the Upper Chesapeake, and Barnegat Bay NJ. During the summer, I was using it almost every second weekend. I still love this thing. I use good NiMH rechargeable batteries in this, and generally sail for about 5-6 hours at a time, with the unit on the whole time to record the track, and to look at the water depths in the rather shallow upper bay. I've never had the batteries come close to dying on me yet, although I do carry a second set of AA rechargeables, just in case. I'm pretty happy with the battery life of my unit. It has been banged around a couple of times (it's tied on a lanyard and hangs off the safety lines of the boat), and landed in the salt water in the wet cockpit of my boat. No problems at all. I've never had it go overboard, so I haven't tested the "floatability" but I'm happy with the reliability of the unit. Also, I tried the geocaching functions fairly extensively. Very cool, and easy to download a lot of data from the website directly to the unit. I'm still very happy with the purchase.