They'll leave marks on the deck. No sun tanning oil. The oil will get on the deck and make the deck slippery, making it hard to stay on the boat. Stowing or putting the boat away is a serious event. Don't take it lightly.
Captains have specific ways to stow the boat.
If you want to be asked back, it's best to follow their lead or ask how they want something put away. Tricks Bring a small line or string to tie your baseball cap or hat to your clothes. You don't make many friends by chasing things that fly overboard. Put sunscreen on before you leave the house. The combination of direct sun and the reflection off the water is very harsh.