Need more slots on the panel Anyway to get around replacing the whole panel
With that panel the answer is no way, I can’t read the main breaker value but I would bet your main 150 at max you have a total of 240 amps of breakers ok 200 because we use the larger of heat / ac so 200 and if the existing water heater is 20 it is two small for a full sized tanked water heater. Even if a 200 and I seriously doubt it. Your service is two small. Are you feeding an inside sub with the 60 for lights and receptacles?