Recently i have use MAC 'eyeliner' this is awesome product....
are soft, smudgy type pencils that 'melt' into the skin. This can be a good thing if you want a soft, smudged look. They are, as you mentioned, tested for the waterline. They can be used on the lash line and inside waterline.
Power Point Pencils
are water resistant eyeliners that have silicones to help them slide on more easlily. Once they 'set' (or dry) they are long wearing. However, they are not tested for the waterline.
Many people look for liners that will be 'waterproof' for the waterline. Unfortunately this is near impossible. For something to be deemed waterproof/resistant it has to be able to dry. Since the mucous membrane on the waterline will always be damp/wet nothing will dry there