Rainy season is between mid December and mid February so bear in mind if you're thinking of getting away during Christmas. The nice thing about going during these months is that the crowds are manageable. Sometimes it may just be you and the divemaster on a dive - no rush, no hassles. We went in early March and although the vis wasn't too good and currents were pretty unpredictable plus the rains would catch up on us from nowhere, it was great for muck diving if micro is what you want. Good diving months are from months April till November. Best diving months is in July and August.