We used Zello when we were down there with a boat. We are just regular people, not part of anyone's navy, just a few guys with a boat that were part of a much larger civilian response to this disaster.
About the Cajun Navy - There were so many people responding to this disaster wanting to help with their time and boats that many times we found ourselves staging to launch but ultimately unable to get in the water because the neighborhood or area we were planning to search only needed 15-20 boats and two or three times that many boats staged for the task. That means dozens of trucks pulling every kind of floating contraption lined up on relatively dry Houston streets and roads and waited in line hoping to be able to take off into the floods and bring people out who needed assistance. When the authorities determined that enough boats had launched for that area, everyone else had to find somewhere else to go. Massive resources were wasted with boats lined up in one spot that could've been actively searching somewhere else.
We ran into a couple of guys from the east coast following Zello Cajun Navy reports who at great expense, drove out to help and had not been able to participate for two days because they were trying to stage in spots where the Cajun Navy was being called up. Once the call went out to the Cajun Navy, boats flooded in from all over and you were nearly guaranteed to have more than you needed. In Orange, we ran into a Texas-based rescue outfit, not the Texas Navy but some group who dressed in military duds. We explained that we were heading into one of the neighborhoods along the Sabine to check a report and asked whether they had already checked it or knew anything about it. They hadn't heard that report or checked that area so we were cleared to go in and the leader of the group asked how we heard about the people needing help. When told that we heard it over Zello, he commented to the effect that the Cajun Navy and Zello was kicking their asses in mustering people and boats.
Fun stuff but the reality of the Cajun Navy effort from our standpoint was that a lot of people wasted a lot of time following their channels and maybe better coordination with other groups would've made a smoother effort.
About the Cajun Navy channels on Zello and Zello itself - Over time the effort evolved into one where each affected area had a dedicated channel to direct boaters to those who most needed assistance. This was not true at the start when the Houston channel had reports from all over the Houston area and eventually Beaumont, Port Arthur, Orange and Vidor too. It was tough at first to determine where the person filing the report was located although there was a website we used to guide us that was actively accumulating requests for rescue and pinning them on an active map. This map evolved to eventually drop many of the requests that were determined to be expired due to rescue already happening or floods receding, etc. We chased reports from that map in the areas that we worked and several times found ourselves following an old report that had not been updated. Obviously, the solution to that is to have boaters radio in and update as they visit addresses. Once the large collection of initial reports from those who had been rescued were tagged or removed the site was much more useful.
A big drawback of Zello in our opinion is that it is vulnerable to manipulation by anyone with the app installed. We kept hearing reports of shots fired at rescue boaters, attempts to steal rescuers boats, rescuers being attacked by residents, etc. and I feel that they were almost all false. We staged at Addicks Dam at the same time reports were actively coming in on Zello Houston channel about shots being fired and boaters were encouraged at the staging area there and later at Bass Pro Shops in Katy to be aware that some rescuers had been targeted. While at Addicks Dam staging area none of us, all Texans and familiar with weapons and gunshots, heard anything remotely like a gunshot. In the days that we were there none of us heard a gunshot at all though the reports over Zello made it sound like you might be taking your life into your hands if you tried to rescue in some of these neighborhoods. A number of rescue boaters were armed and as far as I know none of them had to fire a single shot. I could be wrong though.
Along the same lines Zello was full of reports about imminent dam or levee failures. This got really old as we moved from Houston to Beaumont to Orange and kept hearing the same reports of imminent failure from possibly the same person who kept assuring listeners that the Coast Guard was there with him and informing him that people should leave as failure was imminent. Jeez. Give it a rest. I checked maps around Orange and found that there is no large lake or dam or levee just upstream and we radioed to correct the reports letting people know that they likely applied to Addicks Dam in Houston if they applied to anywhere. Within minutes the same guy came on and announced that the failure of the dam was imminent, the Coast Guard had informed him, etc. A lot of bad information and potentially damaging misinformation was spread.
Anyway. We're home now. Rebuilding will take a while. Help if you can.