Hi Sue,
Safe swimming in the sea depends on the weather. If you've got heavy winds blowing onshore, then you have strong waves and it's not good for swimming.
If you have lighter winds, blowing offshore, then the sea should be flat, tranquil and perfect for swimming.
Weather around boxing day, should be excellent. With the north east monsoon season, the south should be excellent. BUT,,, who can guarantee the weather.
I allways spend some time in the Tangalle area , whenever I visit Lanka and on those visits allways spend plenty of time in the sea. Thats all year round, including July/August, etc in the south west monsoon season. The guest house I stay in is,
The Kadolana Beach Resort, Bandara Watta, Kemagoda, Nilwella.
Thats a lovely rural area between the towns of Tangalle and Dikwella. Great guest house, right on the beach, ..
Head for Matara, thats the end of the south west coastal railway, then a tuk tuk to the Kadolana until you get to know where the buses stop, then they are easy.
The beach is about 1 mile long and usually empty except for a few local kids. If you want quiet, then this place is great.. If you want parties, then head for Unawatuna or Hikkaduwa.
For a compromise, you could visit somewhere like Mirissa. Lovely beach and at this time of year should be good for swimming but in case it isn't, then, at the eastern end, there's a small reef shelterd beach where I've been swimming in the height of a monsoon storm.( quite an experience).
Mirrisa is between Unawatuna and Matara and easy to get to from either direction.
Rod.
