I think the Pelican cases are the best choice overall for the combination of water resistance, usability, and cost. The Pelican 1514 is US$180 at B&H Photo, and comes with a Velcro divider set (avoid the "pick and pluck" foam. Ugh.)
This case is, in theory, carry-on size, though it's right at the limit for full size planes in the USA. That said, you can put a good padlock on it and gate check it when needed, which is (again, in theory) safer than checking it through. I have no experience flying with this overseas. It may end up being too large to carry on many smaller planes.
The Think Tank Airport Security roller is also the max USA carry on size, and actually holds more (I have and use both), but it's not water resistant at all. I would not take it on a small boat to protect gear.