and moreover must be prevented from being immersed in water in this case the structure 6 is constructed beforehand in a tray like vessel 7 this vessel 7 is of pressure resisting and waterproof construction and has a flotation displacement such as to safely carry the structure 6 the succeeding steps of the procedure for floating and moving this vessel 7 and the structure 6 are the same as those described above in connection with the preceding example in still another embodiment of this invention as indicated in fig4 the method thereof is applied to a structure 6a which also cannot float by itself but which may be immersed in water without harm in this case the structure 6a is constructed in the ordinary manner in the construction space 2 then at the time of moving suitable floats 9 are secured to the lower part of the structure 6a to impart the required buoyancy in water thereto thereafter the same succeeding steps as in the first example are carried out to float and move the structure 6a in the practice of the flotation moving method according to this invention the construction of the wall enclosure 4 and the methods of installing and dismantling this enclosure are important considerations the method of this invention can be practiced with full effectiveness of course in a pool or dock which has already been built or has been specially built in this sense the water retaining wall enclosure in the practice of this invention is not necessarily a prefabricated structure intended for temporary erection purposes and.