Here's an easy way to tell: look toward the top of the tube on the heater to see if there's a line that says "Water Level." If there is, do NOT submerge the heater. It's designed to clip on the tank over the top and hang in the water. Just be sure your tank water level stays somewhere close to that line.
Isn't it true that submerging a non-submergible water heater can result in serious electric shock?!
-- Pat
Isn't it true that submerging a non-submergible water heater can result in serious electric shock?!
-- Pat