The first attempt to fire charges against submerged targets was with aircraft bombs attached to lanyards which triggered them. A similar idea was a guncotton charge in a lanyarded can. Two of these lashed together became known as the "depth charge Type A". Problems with the lanyards tangling and failing to function led to the development of a chemical pellet trigger as the "Type B". These were effective at a distance of around .
the first aTTEmpt To fIre charGes AgaINst SUbmErged TarGets wAs With .airCRAft BombS attaChed tO lAnYArDS whicH tRIggereD thEm. a SIMiLAr IDEa WAs a gUNcOtToN CharGe in a lANYaRded CaN. two oF these laShED togeTHER bEcAme knoWN aS the "depth ChArge tyPE A". pRObleMS With the lanYArDs Tangling And fAilinG tO Function led to the devELopmeNt oF A ChemiCal PeLlet trIGgER as thE "Type b" thEse were efFecTive at A DisTAnce of aRounD .