Taylor,

Bass will eat swimbaits in virtually any water condition. At night in water that is mid 40's is not unrealistic at all.

Hydrilla fishing I am not very familiar with... and I don't fish very deep at night usually either. If I was going night fishing anywhere in the country though, the first thing I'd be throwing is the 9" Slammer. I'd prove it to myself that there were no fish shallow before I went deep.

My thoughts are that fish in general move shallower at night, and if they can see or sense the Slammer on top, they're going to at least come and have a look at it. If they're in a feeding mode, they'll probably bite it, and it's not like you won't catch medium and even small fish on it. It's common to catch 1 and 2lb fish at night on the Slammer. They just can't see it well enough to realize how big it is so they bite it to see what happens. If you can't get any bites on the Slammer on top, then I'd just stick with the depth range you are fishing and try to expand your baits by just trying things to see what is fishable in the grass but still gets bit.