Not all locust is the same.

*Black* locust is extraordinarily resistant to critters and rot.
I have never seen it available in plank length, or any other substantial
length.

Honey locust (much more widely available) is not particularly durable (the
technical term for rot resistance).


The two locusts are as far apart in qualities as red and white oak.
The only black locust I have ever seen used in boatbuilding is as trim, as
parts of blocks, and as cleats. It's nice stuff. Let me know if you find
a source for lengthy pieces (or find a way to make your own).