thPaulsen: Your clarification duly noted.
eagle21: It's still a big ocean, but yes, the final impact site may well have been over the Sierra Leone Rise.
Would it be correct to say that if the black box pingers have a range of 2 miles, a searcher would either have to be directly over them at 2 miles range, or at the same depth and within 2 miles laterally? I.E. the slant range would have to be no more than 2 miles total (ignoring the possibility of thermoclines that might change the effective range substantially one way or the other)?