According to the following website quite a few calories can be burned
while gardening. It gives the breakdown as follows for 10 minutes of
activity:

125 pound individual - 41 calories
150 pound individual - 49 calories
175 pound individual - 57 calories
200 pound individual - 65 calories

http://www.spirita.net/diet/calories-burned-chart.htm

I swim about 5 times a week. And found the calories to be as follows
for 10 minutes of swim activity doing a slow crawl:

123 pound woman - 95 calories
170 pound man - 130 calories

Myrl Jeffcoat
http://www.myrljeffcoat.com