When you arrive at Albert's Shipyard for the first time, the game makes sure that you can't leave until you accomplish what you were sent here to do.
In order to be able to get back to the ship, you'll need to talk to Albert, then interact with Albert to purchase the blueprint station from his upgrade store. Once you've confirmed the purchase, you'll need to speak with Albert one last time.
After you do all of that, you should be able to interact with the tender again and get back to sailing!