Meanwhile there are lots of code examples for object-/face-/pose tracking out there on GitHub and Youtube.
Perhaps you should do some research on your own first. If there are still some questions left, you should give us more details on your requirements.
- What kind of ships are you talking about? Large vessels? Hobby boats? Model ships?
- Are you aware of the limitations of Tello flying outdoors (wind, height, WiFi range) and especially flying over water?
- On which hardware do you plan to run the control software?