Some endlessly rolling on river current? (7)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

<=SOM (e) [ endlessly , rolling ] on (River) ESK + I and &lit. Eskimo rolls are moves made in a kayak which involves the kayaker turning the kayak upside down and then righting it again, as seen recently at the Olympics, where it is required in order to navigate one of the obstacles in the race..