Depending what you're after, it is quite a contrast from Istanbul. If the sea is calm, the boat…read moreride is enjoyable. From Kabata pier, it can take anywhere between 75 to 90 minutes to your final destination.
Once, on the island, near the port, it is quite touristy. I prefer heading towards Luna park. Realize it's quite steep. You might consider renting a bike, but I could only ride it halfway as it is quite steep. I saw quite a few people catching a bus or hiring a tricycle to get towards the top with the stunning views.