Question

What are the testes to be conducted on sea water which effects the soil properties

Answer 1

In order to minimize water infiltration into depth you could determine infiltration rates or (saturated) hydraulic conductivities, as well as soil texture, densities and water retention curves. You further may consult models like HYDRUS to predict infiltration under changing conditions like pressure head, solvent transport or even dissolution/phase transitions if you know the minerals and link with phreeqc.

Anyway, how much is "huge"? Do you want to construct a pond or use natural depressions for water storage? You may need more tests to prove mechanical stability if you plan to construct.