Good news for those interested in discovering new species. Researchers have used taxonomic data to estimate the total number of species in a taxonomic group. Using this information, they have determined that there are approximately 8.7 million species of eukaryotes around the world. Of those, about 2.2 million live in the ocean. These findings mean that roughly 86% of species on Earth and 91% of those in the ocean have yet to be discovered!
Mora C, Tittensor DP, Adl S, Simpson AGB, Worm B, 2011 How Many Species Are There on Earth and in the Ocean? PLoS Biol 9(8): e1001127. doi:10.1371/journal.pbio.1001127