This area of the ICW has little more than a couple of feet of depth outside the channel, and the channel itself is very narrow. Just before the storm hit us, a very large motoryacht passed us and moved ahead of us about 1/8 of a mile. Everything on the flybridge, charts, cameras, cushions and anything else we wanted to stay dry, came inside or was stowed away. The rain moved off the mainland and onto the waters just off our beam. Then it hit with a vengeance. The first winds gusts were directly on our beam in the 40- to 50-knot range. The lightning was crashing very nearby, and the rain was coming down so hard we could hardly see the bow of the boat from the inside steering station. All of the channel markers vanished in the driving rain, as did the 80-foot motoryacht that had passed us a few moments earlier. We throttled back enough to keep the boat under control and moving ahead slowly. The only way we had any idea of where we were was by looking at the chartplotter. Fortunately we knew it was accurate enough that if our position showed we were still in the channel, we were confident that was correct. These are the times when the adrenalin is really pumping. Suddenly we picked up an object ahead that turned out to be a green daymarker. There just wasn't any place to pull over and wait. A quick study of the chart on the laptop at the lower helm gave us a moment of hope. Off to our starboard side were charted depths at around 6 feet. More than enough for Beach House's 4-foot draft, IF the depths on the chart were correct. Suddenly the rains let up just a bit and we saw the motor vessel that has passed us pulled off to the exact spot. If he could make it, we could. We turned Beach House out of the channel and maneuvered behind the other vessel, doing our best to just hold position. The whole thing lasted about 45 minutes, but it was a very long 45 minutes.