Yes, it is important to wear sunscreen while deep sea fishing. The sun's rays reflect off the water and can cause sunburn even on cloudy days. Apply sunscreen with at least SPF 30 to all exposed areas of your skin. Don't forget to reapply sunscreen every few hours, especially after swimming or sweating. Choose a waterproof sunscreen to ensure it stays on while you fish. Protecting your skin from the sun's harmful rays can also prevent skin cancer in the long run.