I have one mantra on the boat. It is all about safety. People bring what they want to bring and will dress as they want to. for a day on the water, I'll provide what I have to provide. Always ensure enough Life jackets for all, its my job to be the look out for all and ensure their safety. I plan the itinerary with input from all and set the time of departure and return.
We always start out with a small safety briefing which includes the folowing:
" There are 5 rules of the boat:
rule 1: People in the boat at all times
rule 2: Water outside of the boat at all times.
rule 3: Watch out for the boom, its called that for a reason. If it hits you there will most likely be a loud "Boom" and your liable to violate rules 1 and 2.
rule 4: Help me watch for traffic. Point out other boats, obstacles in the water, etc.
rule 5: Have fun! If your not having fun or enjoying the ride, let me know. We'll figure out a solution."
Other than that I don't ask my "friends" to do to much. And asking them to remember more than 5 rules would be way too much to expect for a fun day on the water.
PS: As to footwear, boat shoes of any kind are OK. I usually pull the leather laces out of most of my boat shoes so they come on/off easier. If you are wearing flip flops or sandals with open toes, be aware that there are things which may cause you to stub toes or loose shoes. Be careful when walking about on deck. Other than Crocs, which I find to be the ugliest shoe ever invented, wear what is comfortable. I'm either barefoot or in Teva's.