Complex sentence: In January 1950, "Finisterre" took part in the rescue attempt of the submarine HMS Truculent, which had sunk after a collision with the Swedish merchant ship "Divina" in the Thames Estuary, resulting in the loss of ten of the submarine's crew.
Split into simpler sentences: In January 1950, "Finisterre" took part in the rescue attempt of the submarine HMS "Truculent", which had sunk after colliding with a Swedish merchant ship "Divina" in the Thames Estuary. The collision had resulted in the loss of ten of the submarine's crew.