No, per USA Triathlon regulations, section 4.9, flotation devices are not permitted during the swim. You can review the rules here: https://www.teamusa.org/usa-triathlon/about/multisport/competitive-rules#article%20IV
However, there will be kayaks, stand up paddle boarders and life guards throughout the water to keep an eye on each swimmer. If you need to you can hold on to a kayak for a few seconds as long as you do not use it to propel you forward.