Two men in workers' gear and colorful hard hats standing on board what appears to be a large ship, next to some very large machinery.
two men in workers gear are on a large ship with machinery
There are two men in workers' gear on board a large ship with machinery.
If the men are on board and they are next to machinery, it is logical the machinery is also on the ship.
On board a large ship is a paraphrase of on a large ship.