A 100-foot-high tsunami wave nearly kills you in your boat. It is likely that:
You cannot tell where you were, because tsunami waves never affect boats.
The question must contain wrong information, because tsunami waves are always long and low and so could not have been 100 feet high.
Your boat was in shallow water near the shore, because tsunami waves are usually long and low out in the deep water of the central ocean, but pile up to become high when slowed by the friction in shallow water near the shore.
Your boat was in deep water far from shore, because tsunami waves are usually very high when formed out in the ocean but get shorter when damped by the friction in shallow water near the shore.
You cannot tell where you were, because tsunami waves are usually very high out in the open ocean and remain high when nearing the shore.