Endless Summer, 1 & 2. Well, 1 is de rigeur- but if you watch 1, you'll prolly wanna check out 2.
And this one might be hard to track down but it's a personal favorite, albeit not really a travel doco . More of a trip.
^ I sincerely hope the remastered version still contains the music of G Wayne Thomas. A real trippy, hand held type movie.