If it has only one entry/exit connection it is a pressure accumulator tank. Your picture only shows one.
A hot water tank will have an upper and a lower entry/exit hole. The hot water tank will also be located on an outside panel and have a removable outside screen.
If the tank is round as it looks, it's a pressure accumulator tank. Likely it held water in the lower half and did not drain when frozen, then it froze and broke open.
Mike
2012 Winnebago Impulse Silver 26QP
2005 16.6 Double Eagle
2018 Jeep Wrangler JK
previously Snowbird Campers,
Triple E Motorhome and Fifth Wheel