The fallout will just give you cancer in 10-20 years as long as you wait to go outside for a week or so. Assuming you’re far enough away that the blast doesn’t kill you, stay as underground or as much to the center of a building as possible for that first week and something like 95% of the rad stuff will have decayed.
Sure some people will get enough dose to die, but more people will get sick and recover. Radiation is not like the movies.
My dad was in the Navy (submariner) in the 80s and he loves that movie. He told me they didn’t do the thing with the string like they do in the movie … Instead they strung it up when they were at depth and took bets on when it would break on the way back up.
You couldn’t pay me enough to be that far underwater.