PURPOSE: To reduce the cost of the title construction by a method in which water in inner and outer annular walls erected on the bottom under water is replaced with a self-setting stabilizer liquid, a reinforcing bar cage is erected into a trench after th stabilizer liquid is hardened, concrete is placed, the water in the inside is drained off, and the inner annular wall is removed.

CONSTITUTION: Inner and outer annular walls 1 and 2 are erected on the bottom 3 under water, corresponding to an underwater continuous wall, and the water in them is replaced with a self-setting stabilizer liquid 5. After the stabilizer liquid hardens, a reinforcing bar cage 7 is erected into a trench 6 formed by the stabilizer liquid on the bottom 3 corresponding to an unit wall, and concrete 13 is placed on the end plates 9 to form an unit wall 14. By repeating the process, an annular continuous wall 18 is constructed, the water in the surrounding of the wall 1 is drained, the wall 1 is removed out, and the top slab 20 of the foundation 19 leading to the upper end of the wall 18 is constructed at the upper opening in the portion surrounded by the wall 18. Finally, a civil engineering structure 21 is constructed on the top slab 20, and the wall 2 is removed out. The needs for constructing an islet can be eliminated.