You wouldn't be the first rower to look like that in uniform. Just where it and focus on your performance.
If it really disturbs you then wear something that changes its position, like a jock, but not if it is uncomfortable. However, not matter what you do you are going to show a bulge straight up or across you leg.
I don't really like the suggestion of tucking it in between ones legs. Men are men, not women, and should not have to go through excessive discomfort to hide their peni. If your white upper middle class, I understand the issues that go with excessive displays of the male body but the overriding theme is always covered and modest to a practical extent.