Salt

If your ramp is made from a hardwood like Mahogany or Fir you shouldn't have any problems. But if your ramp is made from pressure treated Pine, then you will need to apply a sealant. To be extra secure, if your ramp was built with nails apply plastic wood to cover the heads.

Hope this helps.
 
Look what happens to drift wood on the beaches when the sea has had it for a few decades: dries it out. That stuff just gets harder and drier. They key is to not let any water pool in any area - that is what rots your deck. If it's just a ramp and not so,e fancy exotic wood deck you spent thousands on, go for it.