Protecting the head
A cap or hat is a must if you want to stay in the sun for a long time. In addition, a neck warmer, popularized by the Buff brand, is a very practical piece of equipment, especially to protect from the reflection on the water. Finally, it is necessary to complete this equipment with good sunglasses.

Thinking about hands
A pair of gloves quickly becomes essential for a number of destinations. You can use cycling type gloves, with the tips cut off to keep a feel at the fingertips with the material or, for maximum protection, take full gloves.

Solutions for the upper body
Concerning the upper body, there are two possibilities. It is possible to use long-sleeved shirts, which with their flexibility give ventilation and some cooling. The other solution is to wear long-sleeved T-shirts. In the case of T-shirts, I advise to take models with a collar that goes up, this allows to make the connection between the collar of the T-shirt and the neck cover, so as not to risk to catch a sunburn at this vulnerable place. There are also models with a hood or holes at the end of the sleeves to put your thumbs through, depending on your preferences.

Regarding the legs
For the legs, nothing special, except that you must wear pants. There are fishing pants that can be converted into shorts, it is interesting to adapt to the strength of the sun.
Up to the feet
A pair of closed-toe sneakers or open-toe shoes for the water is what is commonly worn. If you opt for open shoes, don't forget to put on sunscreen or wear socks.
The importance of UPF 50
For the majority of the clothes mentioned, you should make sure to take models with the UPF 50 mark. This certifies that the clothing is designed to block UV rays.