Well, this is too touristy but in case you wanna feel like a sultan (!), you can try these kayiks from Dolmabahce palace to Eminönü… If the kayik people would work on their performance, it could be more interesting but now it is only funny and to my naivete I though the kayik would not have an engine. But it does have…. I was told that their website is not updated regularly, so you should have a call to their office… And I see that they have other routes too…