This is what I would call an entry-level mapping GPS. It is therefore one step up from any of the non-mapping GPS units, like the Garmin eTrex, etc. However, there are also far more sophisticated and expensive mapping units than the SporTrak as well. I found this to be an almost perfect combination of price and performance.
This is my third GPS. My first was a first-generation unit that provided very basic position plot information without WAAS (not super accurate).
My second was a marine version of the Garmin eTrex. I loved this unit because it provided WAAS accuracy, was very small, and had a database of marine nav aids pre-loaded. I did not like the fact that it was not a 'mapping' unit, and I did not like its poor reception in non-marine situations (awful reception under tree cover. It was fine on the ocean with nothing to block its line of sight).
So, the Magellan SporTrak Pro Marine is an upgrade for me from that Garmin eTrex. And, it is a big upgrade in my opinion. It is lightweight, splashproof, easy to use, reliable, feature-rich and not too expensive. It is not as small as an eTrex, but on the plus side, you get a larger screen with more data. Most importantly, it provides you with your location in the context of a map! It provides WAAS accuracy. And, it offers far superior reception off the ocean in forests and mountains.
Magellan offers a whole line of SporTrak GPS units. This one is pre-configured for marine use. What that means is that is has a database of all the water navigation landmarks around the USA already pre-programmed into its memory as waypoints.
So, as you're paddling along and pass a nun buoy marked with #7, you'll see it on the screen of your GPS already there. Nice.
It also has a basic street map of the US loaded in, so you'll see highways, rivers, towns, etc. as well.
It provides several different screens to use for navigating to waypoints, tracking your trip, breadcrumb navigation back along your route to your starting point. All excellent. The user interface is very easy to use after some practice.
My only complaint has been in trying to hook it up to a computer to pre-load points and routes and download those to the unit. It was much easier to do this with the Garmin eTrex. I suspect I'm going to have to spend some serious extra money to buy specific Magellan PC software CDs to be able to do what I want. With the Garmin, I was able to use a variety of 3rd party software (TOPO, for example)...
Overall though, the Magellan SporTrak Pro Marine is a fantastic unit for sea kayakers.
While paddling lake Powell, we had stopped for the day to climb out a canyon to the mesa tops. Between two of us was the GPS, I took two extra sets of NiMH AA batteries, we both left the headlights behind for the day's climb, food & water, and some biners and several made steps made from 1 inch tube nylon. Well, we had climbed out of a slot canyon, chimmneyed to a hanging slot, and up that to a curving wall where a series of bolts were driven that led out to a upper canyon and eventually to the mesa top. Turning around, we made our way back, and confident to be getting down through the slots and walls to the inner canyon and most of the way back to where we left our yaks and camp before dark. Getting to the section with the bolts we were stunned to find that someone had taken the nylon steps and biners, leaving us stuck high up. We had no choice but to climb back out and try to figure a way down the cliffs before dark, and after that, get to camp before we froze in the cold. What followed was a freezing, tortuous series of attempts to find a way down the scree and many sandstone walls, without any ropes or protection. How we did it was use the Magellan Marine LCD as a flashlight to find a way down, sometimes lowering it on a 4 mm rope to see the lower parts of walls to see if it could be downclimbed. That night took 7 hours to make it back to camp, freezing cold and shivering, but we got back with only having to change the batteries once. The GPS is waterproof to shallow depths, tough, and makes a tremendous emergency flashlight, too.
Finally, if anyone ever sees someone's ropes or ladders set up, LEAVE THEM, they are expecting them to be there on downclimb. For us we could have fallen or suffered hypothermia because of some dumbshit who took our gear.