Two roughly cuboid objects of similar size. Sure don't look like bits of fuselage. They also look too square for shipping containers.
However it is hard to interpret these images without knowing a bit more about the acquisition. Remember they are sonar images - not visual images.
There are a number of different processing techniques that can be used to improve images.
The shadows (dark areas to the right of the objects) are beside rather than behind the objects. This suggests some form of bistatic system (i.e. separate transmitter and receiver). The transmitter is off to the left while the receiver appears almost above.
https://en.wikipedia.org/wiki/Bistat...dectection.png
Note also the two shadows differ slightly in orientation, but there are a number of possible explanations for this.
One thing is sure. If they are lightweight aircraft containers, there is not a lot of fragmentation or deformation present.