Complex sentence: Zantman's Rock is located 34 miles to the west of the Land's End, Cornwall, near the Isles of Scilly (six miles away) and is barely visible on the surface of the waters.
Split into simpler sentences: Zantman's Rock is located 34 miles to the west of Land's End, Cornwall, and six miles away from the Isles of Scilly. Viewed from a distance, it is barely visible on the surface of the waters.