I would assume water acts mainly as mass but certainly has stiffness and damping properties. Here some initial ideas about its mechanical properties:

https://arxiv.org/pdf/cond-mat/0310219.pdf

A Poiseuille flow regime can act as a linear damper in certain flow / diameter configurations at the right Reynolds numbers.

For spring behaviour I would look at surge propagation in long pipelines. A few 1D numerical codes for water / civil engineering model segments with connected 'spring and damper'-like behaviours.

Hi dear Ahmad, definitely it depends on the structure that you intend to analyze. I attach a beneficial source for you bellow; please read it carefully you will undoubtedly find your answer