The tape may be due to injuries they sustained when crewing. When you're rowing in a crewshell with those huge oars, you might "catch a crab," which means your oar won't come up out of the water when you need it too. When this happens, the oar handle continues into you and might give you a bruise — or worse — right above your navel, where these men have tape. It really hurts when you're going slow, and I can only imagine how fast these guys go.

Look at the second and third guys from the right. Why are their stomachs taped like that?