Yes, your hull below the waterline is solid fiberglass.
Shoot through the hull depth transducers work just fine with solid glass hulls. You just have be careful about location. Any air bubbles flowing over the hull bottom at the location of the transducer will cause it lose bottom lock. A through hull transducer is better, but you still have to position is properly away from items that can introduce air bubbles into the column of water below the transducer. Keep them away from shafts and props and don't mount them behind any under water appendages such as intake or discharge thru-hulls. They need to have clear water to read.