A gas unit that stopped heating is most often a pilot light or thermocouple issue, or a gas valve that’s failed closed. An electric unit is usually a failed heating element or a tripped thermal cutoff, sometimes a bad thermostat. Either way, sediment buildup at the bottom of the tank is a common accomplice: it insulates the burner or element from the water above it, making the unit work harder and fail sooner, which is more common here given the mineral content in South Florida’s water supply.
A popping or rumbling sound, specifically, is usually sediment boiling under a layer of scale at the tank bottom, and it’s worth addressing before it becomes a full failure rather than after. We check the anode rod at the same visit, since a rod that’s fully consumed lets corrosion start attacking the tank lining itself, which is a different, more expensive problem than the part that first brought the tank to our attention.