You can technically swim in Spain in April, but it is primarily an activity for those who enjoy "invigorating" (cold) water. In the Mediterranean regions like Barcelona, Valencia, and Mallorca, the sea temperature typically hovers around 15°C to 16°C (59°F–61°F). While the sun may feel warm on the beach, the water is generally considered too cold for comfortable, long-duration swimming for most people without a wetsuit. The Canary Islands are the notable exception; located further south off the coast of Africa, their waters remain a more pleasant 19°C to 20°C (66°F–68°F) year-round, making them the best choice for April swimming. On the Spanish mainland, April is perfect for sunbathing and "wading," but the true swimming season usually doesn't begin until mid-to-late May when the water finally crests the 20°C mark. If you do dive in, be mindful of the "cold shock" and stick to shallow, sun-warmed coves.