Several beaches along South Florida's Atlantic coast line were closed after thousands of sharks were seen migrating in the waters. The sharks were migrating from Boca Raton to Jupiter since the beginning of March, marine biologists told NBC Miami. Photo: A spinner shark swims just offshore on Midtown Beach in Palm Beach on Tuesday. (Photo by Jeffrey Langlois/Palm Beach Daily News)

Everyone wants to get something for nothing - whether it's a lucky upgrade that means you can turn left when you get on a plane instead or heading off into the economy seats, or even getting a few extra features thrown in for free when you buy a new car.

As some of the sharpest businesses around, no-one understands this quite as well as casinos and that's why they all have a system that they call comps. It's short for "complimentary offers" and these are special treats specially designed to reward you for your loyalty to the casino in question. They're basically bonuses.

A store staff walks past other staffs dressed up as Stormtrooper and Death Star Gunner (R) from the film “Star Wars” before launching the film's new toys at Loft Variety Store in Shibuya shopping district in Tokyo, September 3, 2015. New “Star Wars” toys and other merchandise were released in stores across Japan just after midnight local time during a global rollout of the popular products. (Photo by Toru Hanai/Reuters)

Members of the 2013 “Jarl Squad” take part in the annual Up Helly Aa festival which culminates in the burning of a Viking Galley in Lerwick, Shetland Islands on January 29, 2013. Up Helly Aa celebrates the influence of the Scandinavian Vikings in the Shetland Islands and has employed this theme in the festival since 1870. The event culminates with up to 1,000 “guizers” (men in costume) throwing flaming torches into their Viking longboat. (Photo by Andy Buchanan/AFP Photo)

Close Encounter of the Insect Kind: “Check out the awesome face on this praying mantis. I can't get over the mouth, it's like something from a science fiction movie. Of all photographic styles macro is definitely my favorite. I am constantly amazed, in every photo that I take, by the intricate level of detail that exists on even the smallest of creatures. It's a stark reminder that a very complex and infinitely beautiful world exists just beyond our human-sized level of perception. Photo taken in Donnybrook, Queensland, Australia” – Andrew Young. (Photo by Andrew Young/National Geographic Photo Contest via The Atlantic)

Men ride a motorcycle in front of destroyed houses after Hurricane Matthew passes Jeremie, Haiti, October 7, 2016. (Photo by Carlos Garcia Rawlins/Reuters)

In this September 11, 2014 photo, villagers climb down the side of a hill used earlier as a dumping ground of asbestos waste on Roro hills in Roro, India. An asbestos mine, abandoned nearly three decades ago still affects the people around it and 18 along with Jema were diagnosed with asbestosis in 2012. Tens of thousands more, some former mine workers, remain untested and at risk. (Photo by Saurabh Das/AP Photo)