A simple transit is a line between your position on the water and a static visual reference point either on the water (moored boats or buoys) or ashore (building). If the landscape behind this line appears to be stationary (1) then you are not being affected by the tidal stream. If the landscape appears to be moving to the right (starboard (2)) or the left (port (3)) of the transit then you are being moved along by the tide, possibly away from your original launching position and sailing line across the wind.