If you find your water heater has sprung a leak, the first thing to do is shut the power off to the water heater at the breaker box. It should be labeled, if not you’ll look for either a double 20, 25, or 30 amp breaker. These are the most common sizes. Some water heaters have a switch or are plugged into the wall. If so, just switch it off or unplug it. Next you want to shut the water off leading to the water heater. Check at a hot water faucet to make sure you shut it off all the way. If there is still pressure, then you will have to shut all your water off. There is most likely a shut off valve outside of the house. Shut that off and call your plumber asap! Water heaters here in SW Florida last on average 7 to 10 yrs.