> Keep the ships far enough apart to prevent accidents. Easy! In fact, this is the hard part. Generally, the tanker ship and the ship being refueled are differ

> Keep the ships far enough apart to prevent accidents. Easy! In fact, this is the hard part. Generally, the tanker ship and the ship being refueled are different sizes. They have different handling characteristics, keeping them at the same speed at the same heading is not a trivial task. If there's, say, 1 knot of speed differential, after a minute, now they're 100ft further (or closer) away. Furthermore, ships create wakes which means the handling in the real immediate vicinity of a ship is incredibly different from more or less open ocean. Drift too close, and now the water is literally trying to get the two ships to ram each other, with all the disastrous results that implies.