We are travelling from Istanbul to Athens and then are taking a flight to Santorini. It is my understanding that this is the fastest way to get there.

However, we were wondering if there was a scenic, one-day way to travel from Istanbul to Santorini? How far is Istanbul from the coast? Are there boats that spend a day sailing to the Greek Islands? And, do they go to Santorini? How long is the ride? Cost?

From Istanbul to Santorini you would need to get to Kusadasi which is an overnight bus ride, then ferry from Kusadasi to Samos (2-3 hours if I remember correctly), then a different boat (I think it is an overnighter) to Santorini. Your plan is much better.