There's fantastic surfing on Colombia's Pacific coast, plus fine sailing and windsurfing options in both the Carribean and various inland lakes.
Surfing in Colombia
Colombia's best surfing spots are on the Pacific coast, and Nuqui is the most common base for surfing vacations. There are various excellent surfing spots near Nuqui:
Pico de Loro - excellent surfing a short boat ride from Nuqui.
Juan Tornillo - a short boat ride south from Nuqui, just before Cabo Corrientes, Jaun Tornillo is isolated and beautiful.
El Valle - a small town near Nuqui with cheap accommodation options.
Terco - 20km boat trip from Nuqui.
Termales - rivermouth surfing 25km south of Nuqui, or an hours walk from Terquito area where there are hotels. There are hot springs are nearby.
Also on the Pacific coast, Juanchaco is one hour by boat from Buernaventura. Juanchaco is relatively undeveloped and is good for experienced surfers.
Colombia's Carribean coastline also has surfing options, though the Pacific's surf is far higher in quality. The best months for surfing on the Carribean coast are December to March and July to September. The Carrribean's surf is consistent but the waves are not big. There's various surfing spots near Barranquilla, in addition to possibilities near Riohacha, Cartagena and San Andres.
Sailing & Windsurfing in Colombia
Colombia offers good offshore and inland lake sailing and windsurfing. The entire Carribean coast has sailing possibilities, though Cartegena is the most popular destination. For sailing and windsurfing on inland lakes, Club Nautico El Portillo in Tomine, just north of Bogota is best known. You can also organise sailing and windsurfing on the man made lakes of Lago Calima near Cali, and the lakes surrounfing El Penol near Medellin.