Water Resistant vs. Waterproof

In continuation of terminology week...

On a qualitative level, I know what the difference between water resistant vs. waterproof is, but the engineer in me wants numbers. I mean, where do they draw the line? Turns out, there's a scale - the IP Rating Scale (IP stands for ingress protection). There are 9 levels that cover the spectrum from Gremlin (i.e., terrible awful things will happen if you get the product near water) to Flipper (i.e., you could live in a world full of wonder, flying there under, under the sea):

• IPX-0: No protection.
• IPX-1: Protected against condensation or dripping water falling vertically.
• IPX-2: Protected against spraying water when tilted up to 15 degrees vertically.
• IPX-3: Protected against spraying water when tilted up to 60 degrees vertically.
• IPX-4: Protected against splashing water from any angle.
• IPX-5: Protected against low pressure water stream from any angle.
• IPX-6: Protected against high pressure water stream from any angle.
• IPX-7: Protected against water immersion. Immersion for 30 minutes at a depth of up to 1 meter.
• IPX-8:  Protected against continual water submersion in under water conditions.

* in order to be considered waterproof, the item must have an IP rating of 5+

Basically what this boils down to... water resistant stuff can withstand getting wet (like from rain, sweat, etc.), but shouldn't be submerged in water for long periods of time. Waterproof stuff, on the other hand, is good to go for a swim.