Complex sentence: The first successful use was by HMS "Loch Killin" on 31 July 1944, when she sank "U333"; the system was credited with sinking 17 submarines in 50 attacks.
Split into simpler sentences: The first successful use was by HMS "Loch Killin" on 31 July 1944, when she sank "U333". The system was credited with 17 submarines in 50 attacks.