For background, trace bottom of well-washed sardine tin onto cardboard and a nautical map, and cut out; glue map onto cardboard, then glue inside tin.
Cut waves from blue paper, making tabs on bottom and sides for attaching to can; glue in place. Glue on shells, twigs, toy birds, and cutout images photocopied from sardine label, and cheesecloth for a net.
To make free-floating fish, glue fish cut out to one end of card stock strip folded at each end; glue other end to background.
Brush glue on floor of diorama; sprinkle with sand. To hang diorama, tape rope to back.