I have one of the Ryobi 600psi cordless pressure washers. I don't know it's long term reliability with salt going through it, but I'm flushing it through with fresh water after use.
It can boost either fresh or salt water supply . It can also run off its small hose just dropped off the side or have its pickup dipped in a bucket of fresh water or pre-mixed salt away, boat wash or whatever or run off a 2 litre soda bottle directly attached (but not for long).
It's not a really strong pressure washer, more a higher powered way to rinse things that takes much less effort to set up and move around. But it seems to be working well for that purpose.