Leaving our beautiful anchorage in Ire Inlet, we got a call on the VHF radio from Tor and Jess on S/V Yare. We had spent the previous night anchored near them in the inlet, and leaving at low tide through a tricky entrance channel I had asked them to radio back when they had passed through and let us know the conditions. This would probably work well in most circumstances, but they have their depth sounder set up to read in feet, and to show total water depth. We have our depth sounder set to read in meters, and to show depth below the keel of the boat. Should be easy enough, Tor reports back their depth reading in the channel, I take that number and add 6 for the depth of our keel, multiply that number by 12 to get inches,and divide by 39 to convert to meters, because the only conversion I can remember from school is that a meter is 39 inches. Instead I ignore the whole process, increase the throttle hoping my memory of mass, inertia, and velocity will pan out instead, and barrel through the channel. Once clear of the complicated navigation in Ala Passage, I find the depths rising exponentially when I cut too close to Logarithm Point, and inexplicably make a point to steer the boat in a wide arc around Tangent Island. I consider attempting to triangulate my position, somewhere between Sine Island and Cosine Island, but with GPS I don't really know what I'm angling at and give up. As we leave the math islands I look back and see the slowly receding point that must be Azimuth Island, which might just be the high point of the day.