Are there any regions where you have to worry about low-elevation basins in your landscape that aren't connected to the ocean (such as Death Valley in the U.S.?
Assuming not, the Raster Calculator in Spatial Analyst -> Map Algebra does a fine job with tasks like this. The statement would look something like:
This will test the boolean statement at each cell of your DEM (is the value within the cell less than or equal to 2 meters). If true, then the output cell at that location will have a value of '1'. If false, the output cell will have a value of '0'.
Alternatively, if you don't care about retaining raster cells with values of '0' (those that are above your potential inundation from sea-level rise), then you can use a command like"
This will give you a new DEM, where only cells below 2 meters in elevation are kept (all other cells are ignored - they become 'no data').
Which will do the same thing as the previous statement, only instead of maintaining the elevation value within each cell below 2 meters in elevation, it will just give them a value of 1. If you only care about area of inundation, then this may be simpler than keeping elevation values in your cells you won't use again.
What command you use exactly will depend on what data you have and what you plan to do with the data you produce. You should have plenty of options available to you in Raster Calculator though.
Read more about the tool here: