I'm gearing up for Nations Tri, and would be curious if anyone who has done the race in the past has any notes/tips on the current in the Potomac for the swim. Is it particularly strong? It looks like you are fighting the current for about half the time, so I'd be curious how much of a battle it will be.
I've done it a whole once, last year... after heavy Friday/Saturday storms rolled through. This was my first Olympic race ever and I'm not a good swimmer at all.
I didn't notice a huge boost by going "with the current" after the turnaround. I'd say generally it's not that strong.
River current can change with the tides and rain, so no way to know for sure. Typically it would push against you on the way out, and give you a push on the way back, which is fortuately the longer distance. If its bad, you can swim closer to the shore where the current is weaker.
Looks like the projected tide chart shows that it starts coming in at 5:30 AM on 9/8 and peaks just before 11 AM. So in theory, the earlier you start, the stronger the down river current because it's less offset by the tide coming in.
With that being said, like Sean mentioned it could all be offset by a strong down river current due to rain. There's also the wind direction that may be a factor as well, though some would dispute that. Like he also said, the closer to shore that you are, the lighter the down river current. In general, I've found the Potomac in that area to be on the lighter side current-wise to others (Pittsburgh, Knoxville, Naylors Beach, Colonial Beach, EagleMan) I've done.