If you cannot see tiny bubbles shooting up the side of the carboy, it hasn't started fermenting yet, so go ahead and shake it.
mead doesn't ferment as vigorously as beer...so don't expect to see stuff swirling around inside.
but you can see bubbles going up the sides, like an opened bottle of soda..just smaller bubbles.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10