The driftwood comprises of 2 pieces joined like a pyramid with holes all round the bottom with a total length of 3ft and slightly more than 1 ft depthThey're natural behaviour is to hide a lot of the time, at least when they're smaller.
It might be nicer for your eel if you provided at least a couple of options to hide, especially as it doesn't have sand to bury in.
I bought 5 inch diameter bamboo and filled the bottom with gravel to weigh it down, I cut a few 3inch holes in it with a hole saw and cable tied the top to the rim of the tank so it looks like it just rests at 45 degrees in the tank, my eel sits in there a lot of the day.