Complex sentence: The sea environment is quite rich: there are seagrass meadows, sea anemones, sea fans, corals, moonfishes, and until the seventies of the twentieth century lived here the monk seal, a species which has became extremely rare in Italian waters.
Split into simpler sentences: The sea environment is quite rich: there are seagrass meadows, sea anemones, sea fans, corals and moonfishes. Until the seventies of the twentieth century lived here also the monk seal, a species which has became extremely rare in Italian waters.