Warm up for 10' , After wu, do 4x20" fast with a full recovery between each
Open water swim, preferably at the race site. Look for anything on the horizon that you can spot off of. Throw in few short sprints with full recovery. Just stay loose.
Warm up for 10', make sure your bike is shifting properly and nothing is loose or rattling. Check tire pressure and make sure handlebars, stem, skewers are all tight. After wu, do 4x20" fast with a full recovery between each.