I worked on the 'quarter' form.
I un-smoothed/un-hid all edges in it.
Then it's easier to fix.
I tweaked the Style to have a distinctive back-face color [bright-blue].
I started by trying to tidy it up by moving vertices + Alt... BUT I found it easier to erase most of the really messy bits - lots of short edges etc.
For example - I erased the 'radial spokes' on the corner and exploded the two top curves so that I could see the vertices.
There were too many vertices so I then drew in new edges from the bottom common point to alternate vertices in the top 'curve'; I then erased the edges of the top 'curve' and drew in new edges between the ends of the 'spokes' - these faced.
I also dis some adjustments to the 'prow' end of the 'keel' to get a simpler but equivalent faced form.
Once I was happy I copied the group [Move+Ctrl] and used Scale -1 to mirror them as need; snapped the together grouped the four and exploded them together.
A check for 'water-tightness' proved OK so I use my Volume by Integration tool to find its volume - I did 0.5% accuracy which took ten times longer than 5% accuracy BUT in sqm the result was the same any way!