I won't write anything special about the marina, there are devices for the Istanbul Card, There is a Vapour schedule. You can sail to the Princes' Islands or to the Asian part of the city on Maltepe. (Maybe the schedule and routes are already different, info for 2024.)
A normal marina. Come in - there's a crowd on the ferry, a ship arrives - everything is on it, and after five minutes another one - and you calmly enter the second one. But with all the many people, everyone fits and you can even sit down.