If I understand the seasons in India correctly, you have already been through the rainy season. Don't wait until the next rainy season to get the problem with your drainage fixed. Now will probably be the ideal time to get it fixed. Please get someone who will tell you what to do and then have the work done. The paint on that wall in your beautiful home will keep coming off!

The most important study for you will be the tide levels study & the type of soil that is present on the site. Steel will be the last option if you have no budget constraints but it have to be treated well to survive the water corrosion. You should go for concrete stilts or stone masonry piers but designed in such a manner that the water flow is not obstructed(minimum obstruction) so that the structure you build faces minimum obstruction from the natural habitat(water flow) around. Do keep in mind that such structure can be highly vulnerable for water flooding so be intelligent with the design criteria.

Hi Saibal; Your writing is appreciable. Good. I wish your home is equally good.

Pre-fab or modular houses are easy and quick construction technique, to my knowledge they have a module and the only thing you are asked to get the foundation and base done pre-installation. Hassle free with clean finish and connections.