I was out yesterday and while under way, my depth finder on my Garmin suddenly read 1.3 ft of water and the alarm went off. On instinct I immediately throttled back. I have a second depth gauge on my boat and when I looked at that one I was in 55ft of water. Figured maybe my transponder was being funky, but then a bit later, they BOTH did the same thing and I know I was still in 60+ ft of water. I was following behind a giant tug boat, and there was no way he was in 1.3ft of water. Water was relatively calm, a little chop but nothing crazy and was going about 20mph.