No water most of the way. The last spring is at 1420 m on ascend and than down to 1850 m at descent. Carry plenty of water for 2 days. 

Just parts of the traverse is secured. You must be confident climbing UIAA I difficulty by your own.

Snow conditions in spring or autumn might make it harder with a need for crampons or spikes. Watch for reports and webcam. 

Schema from Bergsteigen.com

The direction via Watzmannhaus is better to split the loop in half. The other way around might be better to climb the scree up instead of down, but the first day is much longer and strenuous (alternatively via log shelters are on the way) .  

Some also choose to climb just to the Watzmann Mittelspitze.

Map of Area