This is a mini submarine for a class at Michigan Tech.
You can pause the print and add three M5 nuts to the inside to make it float upright and self right.
*I printed this with supports for the rear fins.
*Pause at layer instructions:
Use slicer layer view and find the layer that closes the hexagonal voids (around layer 50)
Open G-Code editor and find that layer
Right before that layer starts (indicated by a color change of the line numbers on Repetier Host) add a pause command:
G1 X0 Y0 ; Move toolhead away
@pause ; Pause print
If you are afraid of moving the print head while switching the filament, you can add "G28 X Y" after the pause command to make sure your machine does not lose its position in the x and y direction.