Bartleby
Remembers laughter
are ship movement bonuses culumitive?
If you mean from wonders, yes. Both the Great lighthouse and Magellan's Voyage give 1 movement. If somehow they are both controlled by you and the Lighthouse is not obsolete when you got Magellan's Voyage, then your ships would get 2 move bonus.
This answer is incorrect IIRC. You only get +1 movement if you own both the non-obsolete Lighthouse and Magellan's.
The extra movement from wonders is cumulative with the extra movement point for seafaring civs in C3C though (viz. a seafaring civ with the Lighthouse or Magellan's does get +2 move boats).