Is the seawall able to protect Singapore from getting submerged?

https://www.straitstimes.com/singapore/national-day-rally-2019-100-billion-needed-to-protect-singapore-against-rising-sea-levels

SG is setting aside $100B for some major anti-submersion construction.

Is the seawall capable to protect a region from getting submerged?

Building a seawall is a double-edged sword.  If it can prevent the seawater from flowing inland in the worst-case weather scenario (severe storm), it is effective.  However, if the seawater cannot block out the seawater in the most severe storm, it will trap the seawater inland and the seawater cannot recede fast.

A seawall is not an unequivocal and panacea solution.  We should take a leaf out of Indonesia's book.  The Indonesian president has just announced he is shifting the Jakarta Capital to Kalimantan in the future despite having some major anti-submersion construction including the seawall.

https://www.channelnewsasia.com/news/asia/indonesia-jakarta-flooding-great-sea-wall-11662564

Why is the Jakarta capital moving despite the construction?  This shows that the seawall is not really effective as it proclaimed to be because it is a double-edged solution.

Bangkok is also in the same situation as Jakarta and the Thailand government is also planning to move its Bangkok capital to the north in the future.

Why do these capitals have to move at all if the seawall can block the seawater out?  The answer is crystal clear.