They need a lot of soaking and rinsing to remove the salt and any other contamination
I use a method I found on bird sites. I soak for 48 hours in clean salted water(to disinfect), then I rinse thoroughly and dry. Ive seen some say you should use an iodine disinfectant or similar but im hesitant to do that. The bones do not absorb water your only disinfecting and cleaning the exposed exterior. And they come off the beach sun bleached and pretty spotless for the most part.