How to Understand IP Ratings
IP ratings will tell you how resistant a light is against solid debris and liquids. The first number is the dry rating and the second number is the wet rating. An IP65 rated fixture is completely safe from being breached by solids, and is protected against water jets but not safe to submerge completely under water. The chart below explains this in more detail.
Protected against a solid object greater than 50mm, such as a hand
Protected against a solid object greater than 12.5mm, such as a finger
Protected against a solid object greater than 2.5mm, such as a screwdriver
Protected against a solid object greater than 1.0mm, such as a wire
Protected against dust with limited ingress of dust permitted
Fully Protected against dust with zero ingress of dust permitted
Protected against vertically falling drops of water with limited ingress permitted
Protected against vertically falling drops of water offset 15° with limited ingress permitted
Protected against sprays of water offset 60° with limited ingress permitted
Protected against water splashed from all directions with limited ingress permitted
Protected against weak jets of water with very limited ingress permitted
Protected against strong jets of water with very limited ingress permitted
Protected against the effects of immersion at low pressure between 15cm and 1m
Protected against the effects of immersion at high pressure for long periods of time