To answer this question you need first to check the weather during the time you are going to do your course. between May and September you really need UV protection clothes - long sleeve, light and summer clothes. But just in case bring an extra layer for the night module.
Please do not bring unnecessary items. Avoid metal bits on your clothes. They might scratch the gel coat of our boat.
Bring non marking shoes (white-soled non marking trainers are good).
In colder days: bring nice and comfortable clothes and maybe a waterproof jacket in case it rains.
Besides that: water, hat, sunscreen, mask.
All of these should fit inside a small/medium backpack.