Recently had this happen twice while snorkeling during a surface interval. I get water in my mask and subsequently in my nose. Seemed like I was getting water in my ears as well. Get back to the boat and end up with a major nasal drip (if it was blood they would be getting everybody out of the water!). No problems like this during dives. Only thing I can think of is I do wear a light mustache. Again no problems during dives so I'm thinking pressure is keeping that mask better against my face than with snorkeling. Now I don't want any part of snorkeling. Not quite ready to shave the 'stache.

This is actually quite common when the nostrils come into contact with water. This happens to surfers almost every time they go out. The salt water is so much like human blood that, unless it has little critters or lots of sand in it, it won't irritate your nasal passages. However, it will put on a really cool show when you bend over to tie your shoes or pick something up in front of someone you don't want to be embarassed in front of. The key to prevention in your case would be a good purge mask.