Just an hour's boat trip away from Cartagena lie the magnificent Rosario Islands, which belong to Colombia's only underwater natural park (Rosario and San Bernardo Corals National Natural Park). Abundant marine wildlife (including over 50 species of corals) and some of Colombia's best beaches draw in many in search of relaxation and active pursuits such as snorkelling and diving. Isla Grande is best for kayaking through unique mangrove forests and seeing the phosphorescent plankton light up the waters of a brackish lake at night, while Playa Blanca is Cartagena's most spectacular white-sand beach (also reachable by land). It should be said that the company you choose to tour with has the potential to make or break the experience. Low cost tours can mean multiple intermediate stops en route to your destination, as well as unpleasant surprises such as no transfer back to your hotel. Try and choose a trusted company with consistently good reviews, or opt for a private tour. Mind that seas may be rough at certain times of the year, particularly in December and January, when tours on smaller boats may even become dangerous.

The upmarket marina at Port Denarau has restaurants, cafés and a stage for hosting traditional Fijian performances. Restaurants offer everything from South Pacific and Indian cuisines, to pizza and ice-cream, while there is a spacious seated area with picturesque views across the water especially beautiful at sunset.

If snorkelling and/or scuba diving sounds like your idea of fun, Cartagena is the place to indulge. Waters of the Caribbean washing over this part of the coast hold abundant marine life, including multiple varieties of tropical fish and corals, and the several underwater shipwreck sites make for exciting diving. The archipelagos of Rosario and San Bernardo are both excellent for either.