Hypothetical: You want to do an open water race in the Southern California area such as the Pier-to-Pier swim, the Play Del Run, maybe the La Jolla Rough Water Swim. Perhaps you live as far away as Australia and you too have a swim lined up.
However, a nasty earthquake occurred in Alaska 3 hours before your event and a subsequent tsunami is heading towards your town. So, you really want to do this race but how many hours of racing can you get in before you have to run to higher ground? Well, this Tsunami time map from Moon River will tell you: [link]
More historical tsunami time maps and explanations: [Link]