What would cost such a "aquarium" barge ?

[philgib]

http://www.casadechihuahua.com/barge.jpg

Thanks to MarshMat and MikeJohn for their input

This is for a special use but with a very basic shape :

- Constant 30 inches draft for underwater windows (I will take care of the windows)
- 5.85 meters long at the top
- 5.20 meters long at the bottom
- 2.30 m high
- All made in 6mm
- Strong top structure so that a few people could walk on it without the metal to bow.
- Bow at the front (instead of the vertical flat showing on this drawing)
- The 2 sides must be rigid enough to stand the important pressure of a 30 inches cm draft.
- My understanding is that the displacement would be about 13 m3. Would a 12 cm steel sheet welded inside the barge as a layer on the completely flat bottom be enough to act as a good keel and weigh enough on the boat to maintain the 30 inches draft ? Could anything cheaper than steel be used ?
- Completely empty inside (structure should be right below the very top or inside the bottom keel

Dimensions are such that the barge can fit into a 20' container and can be sent to me.

Would any of you have an idea of approximate weight and building price ?
Of course PMs are welcome.

Thanks a lot

Philippe

[philgib]

http://www.casadechihuahua.com/barge20ft.gif

I have never designed a floating boat before. Does that one makes sense ?