I did the line challenge through the ocean (ultra hand only, no zonai devices, 3 hearts, 1 stamina wheel, no items except those found, no armor, y160-y175)
So couldn't make a raft (and it would have been impossible to go straight with a raft anyhow, I'll explain in a bit) but found wood on the beach. I made a small wooden bridge, and left one piece of wood unattached. I then would grab the wooden plank, place it ahead in the water, go to it, move the bridge in the water ahead, then grab the plank again, and repeat. It was slow but reliable.
Now, the rest wouldn't have been possible for two reasons:
I never used fusion, so even though I did find a Korok leaf and other useful materials for making gusts, couldn't fuse them, and there was no sails either.
The other issue is my path went through a strong current. A raft would have been swept away. The way I got through it was placing the bridge as close as possible on y160, then just barely reaching could put the plank past the current, then. Speed swam and used a stamina dish I got from an NPC I "saved" earlier that was in my path (I just distracted the bokoblin while they slowly killed it, but that apparently counts as saving them lol) to make it back to my wooden raft, then grabbed my bridge and brought it over the current as well to keep going.
A good deal of this was much since I just went into this blind and did it for fun. I thought Lanyru Mountain would be more of a problem but the bokoblin camp had plenty of food I managed to steal and shield surfing let me move fast enough through it to not die while I recovered with food
That must have taken ages, wow ... I admire your dedication ♪
I just went into this blind
Those are the best challenges anyway. Half of the fun comes from encountering problems you didn't expect, and coming up with a solution to conquer them. Always feels a lot more rewarding than just following a script ;)