The purpose of this study is to explore children's typically-perceived-situations (TPS) of "floating" and "sinking". TPS refers to the situation rising spontaneously in an individual's mind when they first think of a phenomenon or concept. Data were collected from 148 Year 5 Korean children. As a result of analysing the data according to three categories--"spatial background", "main object", and "position of main object"--the children mainly thought of a river or a sea with a human or a boat on the water surface or half-submerged as a floating situation; and a river or sea with a boat or a human on the bottom or mid-way between the water surface and the bottom as a sinking situation respectively. Considering the whole context of children's TPS, the contexts of "a boat is on the water surface of the sea or river" and "a boat is half-submerged in the sea or river" were the most frequent ones, as a floating and as a sinking situation respectively. In addition, it appeared that these children's TPS affect their judgment of floating and sinking, in that they showed stronger tendency to regard the situation where an object is just beneath the water as a floating situation, while the position of a main object in their TPS of a sinking situation was nearer to the bottom of the water. Based on these results, several suggestions for science education are given. (Contains 2 figures and 6 tables.)