From the Swim Smart page on the IM site:

7. Warm Up on Race Day

• Arrive early enough on race day for a proper warm-up prior to the start, preferably in the water.
• If you aren’t able to warm up in the water, spend between 5 and 10 minutes loosening up your muscles with arm swings and other gentle movements. A light jog or brisk walk can also help increase circulation and prepare your body to race.

I strongly believe in having a warm-up swim area at a race site, but the athlete information guide did state that an "in water warm up swim will not be available at this years event due to safety measures implemented at this venue" and that participants could swim in the lake at/near the race site the two days prior to the race.

My condolences to the family and friends of our fellow athlete who passed away on Saturday.