You could still be performance limited. The takeoff path must clear all obstacles but also comply with the 4 takeoff segments for FAR/JAR 25 aircraft.
The 4 segments has nothing to do with obstacles and must always be complied with even if the takeoff path is over water.
For a 2 engined aircraft the second segment is the most likely to be the limiting one. In that segment a 2 engined aircraft must, with T/O thrust set and gear up and the critical engine failed, be able to maintain a minimum of 2.4% climb gradient to a minimum of 400 feet.
The configuration changes for each of the segments and the climb gradient required depends on how many engines the aircraft has.