When evaluating both the water-resistant laser polyester and the water-resistant inkjet vinyl, it's safe to say the label itself is indeed waterproof and will not be affected by water. Once printed, the printing is considered water-resistant (resisting though not entirely preventing the overall, long-term effects of water).
Laser polyester is closer to waterproof than any other do-it-yourself label material. Although not recommended for use in a dishwasher, water-resistant laser polyester labels hold up nicely in a shower setting.
Water-resistant inkjet vinyl label sheets are top-coated with a substance that "locks in the ink". Therefore, it is important to achieve a balanced ratio between ink used and top-coating available for locking. If too much ink is used and, therefore, not enough top-coating is available to lock it down, you will see some bleeding when in contact with water. This is easily solved by reducing your ink saturation level in your printer properties box. Always remember to use genuine brand name ink.
Waterproof- impervious to (or totally unaffected by) water, rendered impervious to water by some special process, such as top-coating.