You can easily rent luxury boats and yachts from websites, or you can go to the harbor or their offices and rent one in person. You can check this website to get a general idea on what kind of boats they offer. One of the hotspots to rent boats in person is the bebek beach in Istanbul.
How much does it cost to rent a boat?
Depending on the kind of the boat and how many people it can have on board. The hourly rate for the boat usually starts from 1000 - 2000 Lira! of course, if you rent by the day you'll get better prices as well.
When you rent the boat, the captain and the crew will be with you as well. So, you cant drive the boat yourself XD. If you pay for it, a catering crew will be there to serve you as well.