I think you are confusing the display range with minimum echoes detection. The display ranges is down to 2 meters ~6 ft range on screen but you can see echos within that 6ft of water column. Normally the digital sounders are good to pick up depth as low as around two feet but sometimes you can get under 2. The TZT3 is the same. If you need something for navigational depth I think the Airmar smart sensors get depth till about 1 ft, if that extra foot more shallow matters to you.