It looks to me like you have to remove the louvred panel below the oven. The panel is held on by four screws, one at each corner. The screw covers are probably plastic. I have found that if you gently squeeze the plastic screw cover with pliers the top will pop out, exposing the screw head.
Once you remove the panel, you should have access to the back of the water heater with no problem.
2014 Coachmen Catalina 253RKS
2016 Summerland Mini 1750 RD
2012 F250 Lariat FX4 Crew Cab 6.2L