Anywhere they can reach in time to have an impact. There is no limit on how far the Coast Guard will go nor really a limit on the expenses they will incur to attempt to rescue someone. The US Navy is the same way and the reach is even further. Iu2019ve seen ships leave a carrier battle group to go attempt to rescue a couple civilians on a sinking sailboat out in the middle of the pacific. The Malaysian airliner (MH370) that disappeared a few years back prompted an epic search in very inhospitable waters. Theyu2019re still spending money looking for that plane 4 years later.The Navy and Coastguard sent about 35 ships to Haiti after the earth quake and I can only imagine the amount of money spent on that effort. The Navy has at least two hospital ships that I know about and they regularly sail them to any point on the globe in need of help. Off the top of my head theyu2019re probably each the size of 2u20133 average hospitals in size. If you get out a distress call the US military is going to try and help you if at all possible.