I n the once clear waters of the Caribbean , floating mats of toxic brown seaweed called sargassum blanket the water for months on end, exacerbated by the climate crisis and pollution. The result is a threat to biodiversity and livelihoods, and when it washes ashore, it emits gases harmful to human health, causing headaches, nausea and breathing problems. This pressing, true story is the basis for choreographer Marlène Myrtil’s Océan Brun, informed by interviews with people living in Guadeloupe and Martinique, where Myrtil’s Compagnie Kaméléonite is based. This is the first time the piece has been seen outside Martinique, a move typical of the Let’s Dance International Frontiers festival in Leicester, which gives a platform to global artists every year, all from the African and African-Caribbean diaspora. The tall stone arches of Leicester Cathedral make a stately backdrop for this duet, the daylight through its lofty windows fading over the hour to be replaced by the warm orange glow of stage lighting.…