Much like everything else in your home, your water heater won’t last forever and will develop problems, especially leaks, from time to time. However, you shouldn’t jump to conclusions just yet after seeing that first puddle. Some water heaters “sweat” depending on how they’re installed, and that “leak” you’re seeing may just be an accumulation of condensed water. The only way to be sure is to conduct a thorough inspection of your unit.
If you spotted a leak, see if it originated from the pipes rather than the heating unit. You can easily repair a cracked water pipe by yourself. If the leak is traced back to your unit, see to it that it is unplugged or disabled before getting a closer look. Again, you can repair small, external cracks on your own, although the same can’t be said if the damage is from within the unit itself.
At this point, it would be wise to call a professional since only they know how to properly diagnose the problem. For example, a leaky conventional storage water heater may be caused by a busted dip tube, the component that transfers cold water to the bottom of the tank to be heated. The only way to be certain would be to take the whole unit apart, which is likely beyond your expertise.