No matter what kind of seawall you put in Manila Bay how strong you reinforce, it will just get eventually washed by the strong waves, just like what happens now during heavy rains and winds. The culprit is that the side of the sea facing the Baywalk does not have coastal protection, that is the breakwater.
Breakwaters protect the harbor from strong waves, dissipating energy and momentum from the waves before it reaches the harbor, keeping harbors safe from flooding and tsunamis. But even nature has its own set of coastal defenses.
Mangrove forests also offer the same coastal protection Breakwater Structure does. Manila derived itself from a Mangrove (Ixora manila in Blanco’s Flora), but urbanization decimated those reserves in the Pasig. And I don’t think we could bring back the mangroves in Manila Bay, the bayside has been pulled out of proportion already.