NavList:

Damian Lopez, you wrote:
"I completely agree with Brad. Online sites are good for land use, or for checking on a faraway vessel/port/waterway. The only way to get two-way, real-time visibility of nearby traffic is with an onboard transponder."

The catch is that there are huge numbers of boaters who use those apps, and they're not going to stop just because we tell them that they should. I find when I ask these users that they recognize the limitations and even go beyond them, maintaining a high degree of skepticism. They obviously know that they're not transmitting their own positions without a proper AIS, but that's true of the great majority of small boats (they don't broadcast their positions). The delay is significant, too, but it's also plainly available information: you select the vessel, and the app tells you how stale the position is. This is clearly useful information even with the flaws. If you're in a small boat, and a fog rolls in, an app like that can't show you all traffic, but it can provide some information on some of the most dangerous traffic. 

We can't pretend these apps don't exist, and blanket denunciations of them will fall on deaf ears. But we can try to educate users on their limitations. 

Frank Reed