hamstring cramping

I just finished St. Anthony's Triathlon in St. Pete on Sunday. Although my swim time was ok both hamstrings cramped in T1 when I was putting on my bike shoes costing me 3 minutes as I tried to massage them loose. The water was extremely rough and I was swimming with a new wetsuit. I had consumed plenty of fluids before the swim (Olympic Distance) and had warmed up for 15 minutes in the water before the race start. My right hamstring continued to twitch on the bike for the first 5 miles costing me more valuable time. I've been swimming open water 1 mile 3 times per week for the last 3 months so conditioning should not be an issue. Any ideas or suggestions?

Thanks.
-Allen