Ocean spray is some dense, elastic wood. Watch for rot in those larger pieces. Not always rotted, but sometimes the older stuff gets rot inside from a broken branch above.
The only osean spray bow I finished out was a nice 1" wide 50# at 28", 64" with almost all of its natural reflex (1.5") remaining. I traded it for a guitar, and while I dont regret the trade, I wish I had taken some photos of it first.
While sinew might not be required, it was pretty commonly used in combination with ocean spray/iron wood by Indian/native american/first peoples/indigenous north americans.