The only regret is that many members of the Marmara set sail to do battle and kill Israelis. For them the only regret is that they didn't succeed in killing Israels. The bright side for them is that they set sail for Martrydom (as stated in videos shown) and 9 got their wishes. Israel owes no apology, it is owed one.
At least five killed, 13 injured in Macedonia storm (DPA)
from the article: Israel: We will not apologize to Turkey over Gaza flotilla deaths