Don't forget that the last water taxi to SP leaves at (I believe) 3:30pm, whereas the last scheduled flight leaves at about 5:30 and if incoming international flights have been delayed the flights to SP keep going until there are no visitors left. My record was leaving from the International at almost 7:45pm so getting home by around 8pm.

I recommend people who've had a long and tiring journey from Europe or the far north not even to consider the options but to hop on the plane. If you're fresh, the weather's good and time is not of the essence then the boat can be attractive.