What is the drag effect on swimwear?

[Bede735]

My local pool is 25 metres long and there is a countdown clock poolside, so I thought I would try and sprint as fast as I could. So yesterday I did one length backstroke which clocked 35 seconds, and after a short rest did front crawl in 20 seconds. I was amazed at the difference in the type of stroke used, so surely there must also be differences in the type of suit you wear?

If you swam wearing a shirt and a pair of trousers that must be slower than wearing swim briefs, obviously. So how much slower would you be wearing knee length board shorts? Has anyone tried to make a comparison?