S2CR 18/34 with a horizontally omnidirectional transducer beam pattern is a universal tool for communication in reverberant shallow waters, providing data transfer rates up to 13.9 kbit/s over a 3500 m range.
Underwater Acoustic Modem S2CR 18/34 Product Information, pdf
S2CR 18/34D with a horizontally omnidirectional depth-rated transducer is a limited edition of the S2CR 18/34. The S2CR 18/34D is only available in titanium housing and is depth-rated for up to 6000 m.
Underwater Acoustic Modem S2CR 18/34D Product Information, pdf