LED strip underwater
IP68 indicates immersion resistance to at least 1m (3.2 Feet) or more, as described by the manufacturer. It should be just fine in a pool. Use adhesive heatshrink on the wire connections and coat the ends. 

5V is not dangerous at all. You could put the leads in your mouth and not have any ill effects (except maybe over a week or two...). However, you should definitely have a fuse that will blow if excessive current is drawn. You can buy fuses and fuse holders on amazon. You should use a 2A fuse and a slightly-more-than-2A power supply, if you have one available. Your supply should have enough current to blow the fuse, or you can end up with the supply limiting instead of the fuse.