Antenna in water in HFSS

Hi all
i am designing antenna imerged in water. The fequency is 2.5 GHz. the size of the water-Box is 120*120*160 mm3. Which mesh should be assigned to the water box?


thank you for help

At 2.5 GHz you may expect for PURE water: er'= 78 and er''=20. So tand=0.26 The wavelength in water is around 125/rt(78) = 14mm.
For seawater er" = 38 resulting in less penetration depth and higher attenuation.

Maybe this helps you to find a good meshing.