Whitewater helmets provide about as much sun protection to the face and neck as a baseball cap, which isn’t good. Are there any additions to a helmet that can give better coverage?
how much sun protection do you need?
Wear a heavy waterproof sunscreen and for some shade you can always get a helmet with a brim. The Shred Ready Sherlock is a nice option as it has dual brims which would shade your face and your neck.
For your face and eyes check out the Beak Visor at: http://boc123.com/store/BOC_kayak_store.cfm?category=search As far as neck and ears, as the previous poster responded, sunblock.
Their sunscreens are great – 6-8 hour protection in the water and spf of 36. Also use a full coverage helmet and a visor. You can put a visor on under your helmet and if you want you can get one of those fishing visors with the super long bill.