Time event game script

i was wondering about how to do a time event script for a game. for exapmle:
10 seconds into the game: _root.diver appears
13 seconds into the game: _root.battleship
17 seconds into the game: _root.battleship2
18 seconds into the game: _root.plane
19 seconds into the game: _root.diver appears
24 seconds into the game: _root.battleship

and also, i was wondering how to duplicate and mc, “_root.diver” then place him on the x,y point. if you can at least tell me how to do the above that would be superb!