Experts have mapped which places will be underwater, e.g. https://www.therakyatpost.com/living/2019/11/06/9-msian-citi...
This was semi-confirmed by recent floods. People would say "City X never flooded, it was a drainage issue." But the floods were drawn along these lines, and you can't drain the ocean in the long term.
The 2050 maps are decent to plan around. Even if we slow climate change and turn it around, it might be the state of things in 2075.