Looks like the stern section of an amphibius assault ship of some kind ( just going by the colour and the big hatch in the stern lol ). With real yards building everything in modules nowdays it sometimes near the launch before you can see what the heck they're building !!!
I just cant wait to see the new modules for the new RN Aircraft carriers when/if they're built !! they'll be about 15,000 tonnes EACH thats about the light service weight of one of the Invincible class baby flat tops !!! ( if the new ships are around the 60,000 tonne mark that is ! )
Davie