Edit: Actually a much simpler option is to also download the .ers metadata file and just use ArcMap's (tested in v10.2) regular "Add Data" button to select the .ers file.
SRTM30 Plus data can also be open in ArcMap by changing the extension to .bil and creating a text header file with the same filename and a .hdr extension. A working example for the tile w020n40.Bathymetry.srtm would be a w020n40.Bathymetry.hdr file containing the following:
I'm not sure why
BYTEORDER M works because the .ers metadata file specifies MSBFirst and this should require the
BYTEORDER I, but this doesn't interpret the data properly. Similarly, the GRASS GIS solution by markusN requires the byte swap flag
Further info here: ESRI Help on BIL, BIP, and BSQ raster files