Personally, I'd do some research on them before dropping them into salt water. Some, such as hemite, can rust because of the iron content in it. If you aren't sure about them, or can't identify them and their compounds, I'd suggest going with incense smoke, as Kaos recommended.
I cleanse my crystals on the beach, letting them sit in the ocean while holding them in my hands, or I use non-contact salt, it is known to be a safe method of using salt for cleansing. Do research on cleansing, you will find a method that is right and 'easy' for you, personally, I don't think cleansing a crystal is ever hard unless you aren't up for putting a little bit of work into it if you are serious about the process.
It really does depend on the nature of the stone itself, and like what was said before, its composition. if you know the names of the crystals you bought a quick online search would help, or a consult of a crystal book like 'The crystal bible'.
As a basic overview, any quartz crystal is safe to use running water, salt water, laying a power crystal with it, or 'bedding. Bedding is a more involved process of anointing the crystal with oil, dripping wax over the crystal until it is totally covered, sealing it in a silk bag or other dark material, and letting it rest for a month or full lunar cycle before cleaning the wax off with hot water. Do not use fire or other direct heat as it will assuredly damage the crystal. most of the wax should easily peel off anyways.
More porous stones tend to be softer and/or more brittle and susceptible to damage from water and salt. Others might react to the water by rusting or starting to dissolve.
If in doubt, the best and most universal way of cleaning and charging a new stone is to place it on a quartz cluster in direct sunlight. Clusters are always radiating energy out so it would wash through the new stones. Though you can also bear in mind that there are quite a few stones out there that don't need cleansing, or even act to cleanse other stones they are placed near to or on. Kyanite is a good example, also herkimer diamonds, Moldovite, and calcite as well. placing one of these stones with the stones you want to cleanse in a small bag, or in the sun together, does a pretty good job.
