The water in the snorkel will fall to the level of the ocean's surface. The remainder of the water should be blown out by the diver forcefully exhaling. Some will go out the top and some will go out the purge valve. Unfortunately, purge valves will leak if they get the slightest sand under them. If a leak occurs the diver has to bend the purge valve flap back and rinse all the sand from the area.
Purge valves add to the price of the snorkel.
Check to see how the snorkel is removed from the mask. Some snorkel keepers are in the shape of a figure eight. Sliding them up and down a dry snorkel is difficult. For those, most divers simply leave the snorkel attached to the mask. However, if you have purchased a mask box to store the mask in, it will be impossible to close it with a snorkel attached.