A couple days ago, I decided to head offshore and try to find some dolphin just outside the reef, east of Sombrero Key Light. When conditions are right, the Sargasso weed stacks up in large patches this time of year, and when you find a good size patch of Sargasso weed you will usually find lots of Mahi-Mahi lurking beneath it.
The trip wasn't far from Boot Key Harbor, just 9 miles. The first leg involved passing through Sister's Creek, which is fairly deep until you get to the mouth of the creek, where the bottom quickly comes up to 5 feet. That means I have about a foot of clearance if I'm in the right slot through the channel, which is very narrow. That depth is displayed on my GPS/Plotter and an alarm goes off when I enter the 5-foot zone.
Once outside the creek in Hawk Channel I have two options - proceed down Hawk Channel, or head out through the reef. Heading down Hawk Channel would add a couple miles to the distance, so I opted to go through the reef. Now, I'm one of those individuals that loves to sail through the reef. I love watching the beautiful underwater world unfold beneath the boat, I enjoy seeing big grouper and barracuda fleeing as I approach, and the schools of reef dwellers can be fascinating.
The depths on the GPS plotter, and the locations of the very shallow shoal areas were extremely accurate. When the chart-plotter revealed a 21-foot deep passage through the reef to the Atlantic's azure blue waters, the depth plotter's depth finder and bottom contour information was dead on. It also revealed a 4-foot deep patch of coral that was about 50-feet south of where I passed through the reef, and that's exactly where it was.
I guess my point here is that yes, this information is on the paper chart as well, however, the only visual reference point was Sombrero Light, which was about a mile away. The GPS/Plotter provided pinpoint accuracy, thus allowing safe passage through the reef. The passage area is about 150 feet wide, no one else was on the boat to sling a weight to test the depth, the waves were about 4-feet, thus the captain was glued to the helm in order to maintain course control. In this, and many other instances I've encountered in more than 6-decades on the water, that GPS/Plotter is far superior to paper charts. And, with the 20-MPH winds, that 3X4-foot chart would have blown overboard as soon as it was opened.
I guess from my perspective, particularly as a single-handed sailor, the advancements in electronic navigation are essential tools - not just fancy gadgets or toys. Over the years I've found them extremely accurate and reliable. In my case, I've only had a single GPS failure, which occurred shortly after a near miss lightning strike in Chesapeake Bay, and a Loran-C problem, which was interference during a thunder storm. In both instances, I had no problem finding my way home.
Almost forgot - I didn't find the dolphin, probably because the wind had broken up the organized patches of Sargasso weeds.