A variable tow-depth sparker for use in sub-bottom geophysical surveys. It is mounted on a stainless steel catamaran with flotation for towing behind a vessel. The Dura-Spark 400 consists of 5 arrays of 80 tips allowing the operator to tune the source from the vessel to its application. The typical operational bandwidth of the Dura-Spark 410 is 300Hz to 1.2KHz. When coupled with the CSP-Nv Seismic Power Supply the system offers 2000J/s peak discharge rate, with 5 J per tip to minimise the bubble collapse component. It has a sound output ranging from 0.5 to 1.5 ms.