Complex sentence: Sivertsen 2000: 36 The He 59 proved impossible to remove due to low tide and after attempts to pull it free had damaged the pontoons and wings beyond repair it was towed out on the Leirfjord and sunk on 18 May.
Split into simpler sentences: Sivertsen 2000: 36 The He 59 proved impossible to remove due to low tide. After attempts to pull it free had damaged the pontoons and wings beyond repair, it was towed out on the Leirfjord and sunk on 18 May.