Lateral flucutations of the laser spot formed after passing through a distance of 2.26 km above the sea surface was observed together with the air, the surface water temperatures, and the relative humidity. Our main phenomenalistic findings were as follows: (1) a maximum value of the vertical displacement of the beam spot and that of its time rate were 2.1 m and 0.5 m/min, respectivley: (2) the ''large fluctuation,'' the displacement larger than 10 cm, was likely to occur just before the sunrise and, more remarkably, just after the sunset: (3) in each run of observation the frequency of such a large fluctuation seemed to be correlated with the changes in the air temperature and the relative humidity and (4) an increment of the temperature gradient corresponding to the maximum displacment of 2.1 m was estimated to be 0.77 deg/m.