I was just there a few weeks ago and coincidentally a British family was sitting behind me and the kid was doing this exact same thing throughout the entire ride even telling his dad to do it... wasn’t warned or corrected once by the “Adults”... I suppose those 2 steel guide rails under the water, and the weight of the boat pinching your kids fingers between the two isn’t something Britain’s concern themselves with apparently.
Don’t worry, the British have socialized medicine to take care of them.