I read this in the mid 60's so I would guess it was published either in the 50s or 60s. It is set in the near future (probably with a date that now is in the past). Earth has been contacted. An elite group is being selected to interact with aliens. A trio of bright, talented, and courageous young people are brought together. A hands on marine biologist, hence the shark walking, a historian with an enthusiasm for enactment: the cavalier, plus "a Girl!", who was the hard science person. They along with an alien who is very strong are to go to a test in a huge starship. However the starship has a problem and they have take a lifeboat to the nearest planet with a beacon. It is an earth like planet at about the medevil level of technology. There the facilities on the lifeboat are used to make the humans look like the native species. The alien can't be made to look like the natives and has to be made to look like a pet. The main part of the book is them going on the journey to the beacon. At the end it turns out that the journey was the test.
