Making sense of these numbers
Most consumer devices come with common IP ratings such as 65, 66, 67 and 68.
For example, the Sony Xperia Z Ultra has IP55 and IP58 ratings; it is dust-resistant, protected against water jet sprays, and the effects of submersion in fresh water for 30 minutes up to 1.5m. As of the time of writing, the Xperia Z Ultra is also the only waterproof Full-HD smartphone on global distribution.
Another tough smartphone is the Samsung Galaxy S4 Active, which received an IP certification rating of 67, which means it has complete protection against dust, and is protected against water damage for 30 minutes up to 1m.