Lens for Sony a6700 videography.

Hiya. I’m looking to upgrade from my GoPro 12. And I’m looking into getting the a6700 (open for other suggestions). What lens would be best? I like to shoot reefs and larger wildlife I.e. sharks/turtles/mantas etc. what lens’ would you guys suggest (feel free to comment good camera’s and lens setup for this, keep in mind when commenting I like to edit to slow motion videos.) Any help is appreciated. If you have any questions please ask! (Looking to spend no more than $2500 on the camera and lens, excluding camera housing)