A 'snorkelling tour' would be if you visited different places and went snorkelling in each one. If you are only going to one place, 'tour' doesn't fit. A 'snorkelling trip' could apply to either situation. Same logic applies for your 'buggy' question, although I don't really have any clue what 'buggy' refers to. Like a golf cart? Or a pram? :)

1) tour is the word you want. Let me show you three definitions from CALD (Cambridge Advanced Learner's Dictionary; I urge you to use English-Engslish dictionaries for your level rather than Portuguese-English, esp. in cases like this.) - a visit to a place or area, especially one during which you look round the place or area and learn about it We went on a guided tour of (UK also: round) the cathedral/museum/factory. A bus took us on a sightseeing tour of the city. a tour guide - a journey made for pleasure, especially as a holiday, visiting several different places in an area a cycling tour of Provence They've just come back from a tour of / round Devon and Cornwall. Tour operators (= companies which arrange holidays for people) have reported a drop in bookings. - a planned visit to several places in a country or area made for a special purpose, such as by a politician, sports team or group of performers "Trip" is a journey as well, usually a short one when you come back again, but this word is less specific.