Complex sentence: Ivanović was also an avid scuba diver and wrote several books on spearfishing, of which the 1975 edition of "Modern Spearfishing" remains a classic.
Split into simpler sentences: Ivanović was also an avid scuba diver. He wrote several books on spearfishing, of which the 1975 edition of "Modern Spearfishing" remains a classic.