There wasn't really a discrepancy in response though, and if you are lost at sea and have nothing to hang onto...you aren't going to last long. I saw someone ask why the US didn't send ships to look for migrants, well...that's a 10-day ride across the Atlantic & Mediterranean. Even surrounding countries were sometimes hours away.

The average human can't tread that long without a life jacket, the average is ~2-3 hours and that's in still water (to be a lifeguard you have to last 30 minutes), not a choppy ocean/sea. By the time any country other than Italy or Greece came to the location, they'd already be dead. It's tragic, but there is no discrepancy. If there were a chance of actual survival for days, there would have been a much larger response.

Also, apparently the Greeks offered aid before the boat even sank and the boat declined because they didn't want to go to Greece, they wanted to go to Italy. There are mixed reports on that though as now some are blaming the Greek coast guard for tipping the boat over by accident.

If you want something to be upset about, be upset about practically every country on Earth's broken immigration systems that cause these tragic events.