Not only do fish and invertebrates make their own sounds, but wind, waves and currents also create other background noise. And reefs especially are naturally noisy places.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/noise-pollution-affects-coral-reef-fish
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/environment-news-network
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/noise-pollution
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/environment
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/corals
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/fish
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/marine-ecosystems