As you may or may not know, my home city of Calgary, Alberta has had a very bad flood recently. Our local annual Big Show, The Calgary Stampede, is selling t-shirts for flood relief - Calgary Stampede t-shirts - Hell or High Water! From what I saw on the site, it looks like they will ship them to at least the US, Canada, the UK, and Australia (those were the top four countries listed).
The slogan is in relation to the fact that the Calgary Stampede grounds were badly flooded last week, and there were questions about whether the Stampede would actually be able to go ahead for mid-July, hence the “Hell or High Water” slogan. As of now, there are no plans to cancel the Stampede; everyone is working frantically to get it cleaned up and ready to go. 
