It’s a trap!
The Wakandans trick Namor and the Talokanil into attacking their boat, starting a large fight between the two countries. While Shuri attempts to capture Namor, the Dora Milaje repel boarders from the sides of the boat.
While this sequence is made up of a lot of visual effects, the platform and sides of the boat were filmed at an outdoor location separate from the studios. The back lot area at OFS Fitel in Norcross, GA served as the staging area and outdoor set for portions of the film, including the stunts on the side of the ship. The original Black Panther film also shot here, replicating part of Warrior Falls.
(Black Panther: Wakanda Forever, 2022)