Hi,
I've been to Donsol last February. Here's what I can tell you from my experience.
If you are from Manila, you can take a flight to Legazpi. From there, it's about
2 hours drive. The whale sharks gather at the bay of Donsol from February to
June. It's one spectacular place, and I'm sure you'll enjoy swimming side by side
with the giant.
When you first arrive to the place, you are required to watch a video informing
about the place and shark inside the managing office built by WWF. After that,
you'll be paying a conservation fee and boat charter fee. You'll board the small
boat with boatman and a guide. Boatman will locate the shark, and once guide's
approval has been given, you are allowed to swim with the giant. Sometimes
you can swim close to an hour with the shark, but most of the time, they will
dart through the murky water. Don't worry though. You'll have plenty of chances.
I think I was on boat around 8AM to 11AM, and saw more than 10 different species.
If you will be visiting the place Feb to Mar, bring a thin wet suit or rashguard. The
water temp is about 23 to 24C. Also, bring your own mask, snorkel, and fin. Fin
is especially important since those giants are fast swimmers eventhough they are
just crusing to feed on plankton.
There is an accomodation in Donsol called Fernando's Hotel. There email is
fernando@k-net.edu, but I'm not sure this address is still working. I believe
they can arrange whole trip if you have no idea about the area.
I'm planning to visit again next year, but seems like the volcano up there is getting
a bit active again... Good luck!