Cape Cod Canal, what is on the bottom?

[BassyiusMaximus]

I go over the canal, drive alongside of it, but have never fished it and to the delight of most of you, I might never fish it.

My question is, what is on the bottom of that canal? Is it sandy? I mean, when they dug it out and before the water ran through it, it must have been just sand or dirt on the bottom and I can only imagine that over time the sand and stuff washed away to leave behind a boulder/rock strewn bottom.

I ask because I see that many jig the canal, and if you do, how in the world do you do it with all those rocks down there, or do you accept the losses and try not to get hung up. Are there areas that are sandy on the bottom or is there no such thing since the flow is almost always and has been present?