When I was 20, I'd say basketball, for me. I could run the 400 pretty well, but obviously I'd be nearly 100 m behind these folks. At 1600 m, I once broke 5 minutes, about killed me, unofficial time, but that puts me over a minute behind, an entire lap. Things like shooting would not look as terrible of course even if the score was a joke. I'd look OK. Swimming? I probably wouldn't drown, again, I'd be laps behind in most events, if I could swim that far at all.
Anything diving or gymnasticly, fuggit aboud it.