I am not fully sure if this is what I think it is, but as I see it this place here is to let boats via trailer into the water, right?
If so, I think the piece that is on the bottom of the ocean should be translatet upwards a bit.
https://abload.de/img/20160610173644_15eoew.jpg
https://abload.de/img/20160610173647_1a7r9y.jpg
https://abload.de/img/20160610173650_1w5oy4.jpg
http://up.picr.de/2456390.jpg