Nice design! I feel your pain...I'm forever designing things with no idea how I'm going to actually construct them. That's part of the great adventure for me.
For yours, I'd definitely go with partial seams for the small boat elements and use a braid-like sequence of adding straight segments. I'd have the corner anchor attached to the shorter boat section to give me more flexibilty (longer piece) going around the triangles. The blue triangle bases can be sewn to the 'under' units in advance if you're sure of your measurements or 'as approached' if you're not quite as sure. Either way has a bit of a risk for distortion but is easily fixable if caught before moving on. To add the dark blue borders that square the whole thing off, set in (Y) seams would probably be the best option.
I hope that sparks some ideas for you. When faced with pieces like this, I've learned that it takes less time in the long run if I hand baste each section first to make sure it's going to fit/look right. It's much easier to take out basting than machine stitching and there's less stress to the fabric. Good luck to you!
ETA: Another option would be to just make two full squares of the small boats, slit one at an 'under' point, weave them together as one unit, and then stitch the whole thing with inset seams onto the octagon of your central piece. You'd have a double layer of fabric at each crossing point, but it
is an option.
OR...do that and then trim out the overlaps so it's just one layer...hmmm. I can't seem to stop........
