Jeremy,
I'm not Mike, but here goes...
Hard to tell because I can't see the size from the picture, but to me it looks like an East African Mangrove Crab (Cardisoma Carnifex). What is notable is the dimorphic claws, the heart shaped body, and the hairy looking legs. The adult has a carapace width of around 10cm.
Ed
ps Nice shot btw.