The tendrils of this stuff exceed 12 inches with blubs near the end. It flows near the surface in mats and in my instances it jammed into the engine intake hole between the outer hull and the sea cock ball. To clear it the mechanic had to remove all the piping, a elbow and the top of the seacock itself, then jam a wire hanger down from the top of the seacock. This is all before (upstream) of the sea strainer.
Just today a tendril worked itself into the intake of the head and into the flush-dry valve requiring the same kind of process.