Be careful on Tschida (or any western ND reservoir) for the next couple weeks. The warm weather we had a little while back has produced runoff and shorelines in particular may be a little iffy as incoming water rots the ice and rising water levels lifts the ice along the shore.
In particular, Tschida has come up about half a foot so far. While this isn't a heck of a lot, it's not nothing.
Oh yeah, and I too think the above pic looks like the guy encountered a pressure ridge. Those are always hairy...