Bava Batra 76 - Acquiring a Ship: Control It, Pull It, or Lift It?
By (Torah) law, when one pays money, he acquires the object. The Sages, however, established that movable objects should be acquired by lifting, pulling into one's domain, or taking control over them. Until the buyer takes delivery of his purchase, the seller, who already got paid, may not be careful to protect it. If, however, the object is still the seller's until delivery, he will be careful.
If the ship is on public grounds, one cannot pull it into his domain, therefore, the seller can give control over it to the buyer. If the ship is in an area which people can use as their own, the buyer should pull the ship into his domain. If the ship is not afloat, one can lift it or rent the area under it.