Paul O'Donovan and Denise Walsh were both winners of their respective lightweight single sculls semi-finals at the World Rowing Championships in Florida.

Reigning champion O'Donovan produced a customary late surge to move from fourth to first place with 700m to go.

He came almost four seconds clear of Switzerland's Michael Schmid in a time of 6:55.30.

Walsh also led home her rivals, finishing in 7:45.89.

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"Especially in the single scull, there's no panic to hit to front," O'Donovan told RTÉ Sport. "The winner is only decided at the end.

"I was sitting up in the leading group and knew I was feeling good so I could push through then when I felt like it.

"I wasn't at my maxmimum there yet so we'll try and give that a go tomorrow and see how it goes. But I don't think the rest of them were either today."

Irish boats are in three medal finals tomorrow.

Mark O'Donovan and Shane O'Driscoll go in the lightweight men's pair at 5pm Irish time, Paul O'Donovan rows at 5.15, and Walsh at 5.30.

Sanita Puspure is also in the women's single sculls semi-final at 4.15pm and Fionnan McQuillan Tolan and Patrick Boomer go in the men's pair C final at 6.50pm.

Watch the World Rowing Championships live on RTÉ2 and RTÉ Player from 3.30pm on Friday.