How many degrees does Sanya go to in early April? Is it okay to swim outdoors?

At the beginning of April, the temperature in Sanya was generally around 25-28℃, but this year's temperature was a bit abnormal, and I felt very cold all the time. Sometimes the temperature is as low as 15℃ this month. As long as the weather is good, you can swim outdoors at ordinary times, and the water temperature in the swimming pool is OK. If you go to the seaside, you may be a little cold because of the strong sea breeze.