If Mythical Creatures Existed No. 1: Mermaids

The existence of mermaids would be a massive boost for our understanding of the sea. Assuming they were not hostile to humans, we could learn a lot from them. If they were hostile, they could cause some real damage. Our shipping would be in danger, and due to their ability to talk to fish, there is a real chance a large part of the world's food supply could become unavailable when the mermaids tell them how to avoid our nets.

However, I would like to think they would like to coexist in peace with humans.
Here's a list of some of the benefits they could bring to our civilisation:
- Deep sea exploration. They would have a much greater knowledge of the darkest places of the oceans.
- Sustainable fish farming. They could herd fish into suitable collection points, making the hit-and-miss approach of deep-sea fishing redundant. The mermaids would also be able to keep track of fish numbers, meaning we could change which fish we herded depending on their sustainability.
- Wreck location. This would be a great help to the families of those who have been lost at sea. They could also help recover ancient artifacts, and would be especially useful in underwater archaeological digs.
- Scientific knowledge. Through careful study of mermaids we would be able to better develop biological technology that would allow humans to survive underwater for longer periods of time.

Of course, we would need to provide things in return:
- The technology to allow mermaids to visit land. They would get to see parts of the world they had never experienced.
- Jobs. Depending on the employment situation under the sea, they would be plenty of work opportunities for mermaids. From fish herding, wreck locating, to entertaining guests at island resorts. The most beautiful among them would almost certainly land key roles in films and television series.
- A greater respect for their home under the sea. Due to a dialogue between the two races, the sea would be able to be managed better and to the satisfaction of all parties.

Cultural impact:
- Books, movies, websites, television series and toys based on mermaids would spring up almost instantaneously. Key themes would include "love that can never be" and "lessons we can learn from each other".
- I estimate it would take 0.035 seconds after the discovery of mermaids for a human to wonder whether it's possible to mate with one. That's up to the scholars to decide.
- Literature and media exchange. The two cultures would have a lot to tell each other in terms of stories and artworks, with the possibility of finding similar universal themes and stories that resonate with both races.

If anyone else has any other mythical creatures they would like to see, let me know!