Actually where will you go? 大阪?白浜?
In summer holiday, I went to Osaka, 和歌山,白浜,勝浦for 10days
Hotel seamore also located in 白浜,if you have more time ,I highly recommend 勝浦温泉,but it takes 2 more hours by train from 白浜
Some famous hotspring are located more nearby such as 有馬温泉