This was the first place I've really visited where English was not the primary tourist language. We'd walk down the street and people would get our attention by shouting offers in Russian first, then english when we didn't understand. Tons of signs were Vietnamese and Russian only. The beach was more than 80% Russian.
For me it seemed like the Cancun of Russia, Karin said the same of Germans and Ballermann. It was fun to people watch here but I can safely say we never need to return.
One new thing we did was a mud bath. Unfortunately we took no pictures but it was interesting: we sat in a pool of minty mud for about 20 minutes, followed by very hot bath for 5 minutes, then the rest of the time is spent in a more normal thermal bath area with several pools. They had nice fake waterfalls of mineral water too.
We enjoyed the downtime, but Nha Trang is a pretty neutral place overall. After a couple days moved on via nightbus to Hội An.