Harold swimmed one hundred laps in the pool yesterday.
I'm glad Harold swam all those laps! Good for him.
I don't know what your question is, but "swimmed" is incorrect.
http://www.bing.com/search?q=past+tense+of+verb+%22swim%22&form=EDGNTC&qs=PF&cvid=f905c3083a7e46fd8d38b554da377ee1&pq=past+tense+of+verb+%22swim%22&cc=US&setlang=en-US
The correct past tense form of "swim" is "swam." Therefore, the correct sentence should be: "Harold swam one hundred laps in the pool yesterday."
It seems there is an error in your sentence. The correct past tense form of "swim" is "swam," not "swimmed." So, the corrected sentence would be: "Harold swam one hundred laps in the pool yesterday."
If you have any further questions or need assistance with anything else, feel free to ask!