There are two types of oaks, the "whites" and the "reds" in this country. Both are used in the boat building industry.
Typical uses for the reds are in deadwood assemblies where continuous submersion can be expected. In this environment
, it's a weaker and lighter alternative to white. It's also not as likely to rot
in this application. This said, most of the reds have a tendency to rot at the mere mentioning of moisture, as has been noted above. It's interconnected cellular structure can wick moisture through the body of a piece, which isn't good. If well protected or used in locations where very limited direct water
contact is present, it can be successfully employed.
Of the whites, plain old white oak (Quercus alba) is an industry standard, but not the best choice among the whites. Live oak (Quercus Virginiana) is hands down superior in every regard. It's denser (the densest wood in North America), it's stronger, it's more rot resistant, it's less prone to check/split because of an interlocking grain, it's heavier, etc.
To answer your question about the leeboard bearing blocks (I'm assuming), I'd be inclined to agree that red oak isn't the best choice, mostly because it will wet/dry cycle a lot and red doesn't like this much, without issues. This isn't to say you couldn't use it, you can. The blocks will be well above the LWL so only intermittently soaked. If you provide an epoxy
pivot bearing, encapsulate the piece well and keep an eye on it's condition, then you could get away with red oak. It wouldn't be my first choice or second, but it can work.