Complex sentence: The strong currents around the island provide for an abundance of marine life, particularly on the north coast where the depths reach 15 metres, and many people enjoy fishing trips departing from Beaumaris in these waters, catching mainly mackerel, but many other species are caught.
Split into simpler sentences: The strong currents around the island provide for an abundance of marine life, particularly on the north coast where the depths reach. Many people enjoy fishing trips departing from Beaumaris in these waters, catching mainly mackerel, but many other species are caught.