From the 9/6 New Scientist, in a letter from Bruce Denness (p. 28):
The tank shallowed towards one corner so that deep-water waves … began to break as they approached the shallow corner.
That’s the inchoative verb to shallow ‘to become, get shallow(er)’ — a direct verbing (or zero conversion) of the adjective shallow. I’m not agin verbings (unlike a number of peevers, who are driven into rages by them), and this one serves a real purpose, but it was new to me. It’s also venerable, and has even made it into NOAD2.