Unfortunately, the best time for sailing and fishing
, snorkeling or just hanging out at the beaches are not the same. Best time for sailing is during the southeast monsoon from about May to September (peak in july-august). This is the dry season here, with good, strong (15 to 40 knots) and stable winds. Normally there are no storms during these months. The plateau where Seychelles Islands are located is relatively shallow (about 60 m average); the strong winds keep the water
stirred and turbidity is higher, so snorkeling, diving
, swimming, etc. are not that great (not bad either, just not as good as they can be). Beaches, especially those facing the south are also rougher. The rest of the year (October-March) is the rainy season with the so-called Northwest monsoon. Winds are soft and shifty most of the time (so you should be prepared to do a lot of motoring if necessary), and with smaller storms once in a while (we are right on the equator, so no big storms ever get here). This is the best time for fishing
, snorkeling and diving
is exceptionally clear and seas are calmer. You can also basically anchor
anywhere, but with the southeast monsoon you are limited to protected anchorages
(those facing north or inside the lagoons). That should give you short of a general idea, and I think it basically nails down to what your main interests are. If sailing, come during the southeast. If snorkeling/diving/fishing is what you enjoy the most, come during the northwest. You might be able to get the best (or the worst) of both if you come right in between monsoons, my best experiences sailing/diving and fishing here have been around May/June. I have had the best ever dives in December-January. In your case, since you’ll be here for a limited amount of time, you also have to consider that coming during the rainy season might get you here during a rainy week, not uncommon.
Hope this helps. If you have any more questions, I’ll be happy to help.