After spending some time at the Osa Peninsula we will probably go back via private shuttle form Sierpe to San Jose Airport. Do you know at what time the boat leaves from Bahia Drake to Sierpe (as on the form on your website one needs to mention a pick up time for the private shuttle in Sierpe).
The boat schedule from Drake Bay to Sierpe is at either 7:30 a.m. or 2:30 p.m.
If you are returning to San Jose that same day by shuttle, we would recommend the morning boat. The boat shuttle takes about 1 hour, so if you arrange the shuttle through us, we would have the driver there waiting by 8:30 a.m. Hope this answers your question.