Went out fly fishing for Sandbass today and could not get my flies down deep enough to get to the Sandbass what fly line would y'all suggest

How deep are they? If not too deep a Airflo fast or super fast poly leader might help or maybe a full sinking line.

10-15 feet

10 to 15 feet is deeper than most fly fishing setups will effectively reach. It is difficult to fish that deep with a floating line and poly leader.

You can get to 10 feet or so with a long-ish headed sink tip line. The head needs to be longer than the depth you are trying to fish. The sink rate of the line depends on how fast the water is moving. In fast moving water, you'll need a fast sink rate to get to the strike zone before the line is moved down stream.

To get to 15 feet, I'd probably either get a sinking head setup or a full sinking line. Where are you planning to fish? I personally don't like using full sink lines or heads in rivers, because I tangle them up too often.

Rio makes Versi leaders. 12 to 15 dollars a piece. I think they have a loop on one end to connect to your fly line, if not a perfection loop will solve that. I like them because you can change them out quickly. They have a variety to choose from. It's better than having to buy a new fly line.

Got down that deep to the really big girls on the Sabine with floating line. That is if you don't want to dump 90 bucks on a line you don't have many other uses for. I just used a little bit longer leader and added 3 foot of floor carbon and put three panfish size split shot up above it sunk a Clouser like a rock and I caught plenty of fish. Just trying to give you an alternative because I know there's very few times in the year I am like man I wish I had a sinking line but that's just me. Now it definitely is a chunk and duck if you are not very proficient in casting. Leave a good knot if you caught the back of the head lol.