the new project i'm martina mcbride is called "everlasting."want to add this to your collection. have a great to her. good to have you on. that's our show for tonight. thanks for watching. as always, keep the faith. >> for more information on today's show, visit tavis smiley at pbs.org. tavis: hi, i'm tavis smiley. join me next time for a conversation with comedian tim conway. that's next time. we will see you then. ♪ >> and by contributions to your pbs station from viewers like you. thank you. >> be more. pbs. captioning sponsored by wpbt >> narrator: six years, 22 countries, close to 200 scientists, and one exceptional research vessel. the global reef expedition is on a mission to study coral reefs around the world. >> coral reefs are undergoing a worldwide crisis, and we are trying to understand where the healthiest reefs remain, what sort of factors make those reefs healthy, and, reefs that have been degraded, how we can help them recover and persist into the future. >> narrator: to do so, expedition scientists conduct a number of studies i