Would a life jacket help if a tsunami strikes?

Not much: If you are struck by the major aspect of the tsunami wave, the life jacket will be of little help. If you are at a low velocity, low volume edge of the wave it might give some help. The best way to be around a tsunami is to be somewhere else or be incredibly lucky.

Tsunami: A tsunami's danger is not just from fast moving currents but also from all the debris it contains. Although a life jacket may offer little help - If I was stuck inescapably from the path of a tsunami - I would pray and put the life jacket on. Bottom line- don't count on a life jacket to save you.