Mystery of the group of 100,000 dolphins spotted swimming together off the coast of San Diego A group of over 100,000 dolphins spotted off the coast of San Diego caused a spectacle for nature watchers as they traveled together in an enormous pack. 'They were coming from all directions, you could see them from as far as the eye can see,' Joe Dutra said after seeing the spectacle first hand. Mr Dutra, who captains Hornblower Cruises, was out on his daily tour with a boat full of nature watchers when he spotted the massive group of dolphins. Massive group of mammals: A ship captain spotted a group of 100,000 dolphins swimming together off the coast of San Diego on Thursday and experts are unable to give a specific reasoning for why such a large group would be there 'I've seen a lot of stuff out here... but this is the biggest I've ever seen, ever,' he told the local NBC affiliate. Dolphins typically travel in groups of anywhere between 15 and 200 which are called pods. What Mr Dutra spotted on Thursday however is best described as a super mega pod given the astonishing size of the group. He estimated that the trail of dolphins was seven miles long and five miles wide, and he was able to steer the boat alongside them for over an hour. Experts are unable to pinpoint any specific reason as to why so many of the mammals were traveling together on this particular night. 'They're definitely social animals, they stick together in small groups. But sometimes, the schools come together,' marine expert Sarah Wilkin told NBC. Spectacle: The group was supposedly seven miles long and five miles wide While it does seem like a once-in-a-lifetime experience, a very similar flock of thousands of dolphins were seen swimming together about this time last year. At the end of February in 2012, an unspecified group of dolphins was spotted swimming about 65 miles north of San Diego, implying that there may be an unacknowledged migratory pattern.