Complex sentence: Tintin, however, realises that the meteor could be protruding above the surface of the water, and the Professor is persuaded to organise an expedition led by himself to find the metal and to retrieve a sample of it for further research.
Split into simpler sentences: Tintin, however, realises that the meteorite could be protruding above the surface of the water. The Professor is persuaded to organise an expedition to find the metal and to retrieve a sample of it for further research.