Complex sentence: There are many smaller islands, islets, rocks and reefs in the bailiwick which combined with a tidal range of 10m and fast currents of up to 12 knots, makes sailing in bailiwick waters dangerous.
Split into simpler sentences: There are many smaller islands, islets, rocks and reefs in the Bailiwick. Combined with a tidal range of 10m and fast currents of up to 12 knots, this makes sailing in local waters dangerous.