Hopefully some readers can comment with their own "that guy" advice, but this may amuse...There is something that sets off distant summer memories in the squeak of a styrofoam cooler lid. Granted they are practically worthless unless just sitting there on the table, you can't really lug stuff around in them or risk the inevitable crack&spill of ice, beer cans and maybe some trout and fishy water... The absolute worst I ever saw was a group walking on the beach in front of a lifeguard tower, who managed to crack, spill, drop their cooler full of beer bottles which then smashed. It was the perfect storm of "that guy". Don't bring glass bottles to the beach... don't let them smash... and for keee-rist's sake don't smash them at the foot of the lifeguard tower where they have to jump down in the sand. Forget that "no alcohol" signs are posted all over the place, that is icing...
At the very least:
1) get a decent cooler.
2) bring cans. That isn't too much to ask is it? And while you are at it leave the lacrosse sticks at home...
