If the Navy were concerned about it, they would send a flotilla out to escort them.
This is just an example hollow saber-rattling that Iran's leaders are engaging in in order to look tough on America, its no coincidence they are doing this right after a preliminary deal with the US. People seem to forget that we placed and kept a ruthless dictator in power in Iran for years, much of the Iranian populace is still angry at us for that. From a unbiased point of view, we do seem to have a compulsive need to meddle in the Middle East (a lot of it unwarranted, I may add. Such as Iraq), but Iran is different, in my opinion. If Iran made Nukes, that would upset the delicate balance of power in the region, and potentially create a mini- nuclear arms race in the Middle East, which would NOT be good in such a volatile region. To get back to the point, Iran's Leaders need to look like they are staring us down if they are to keep popular support, and continue negotiations. It would be best to let their pitiful excuse of a fleet sail around a bit and go home to be congratulated for their "daring actions".
Neither side in an argument can find the truth when both make an absolute claim on it.