This is the dramatic moment several crocodiles appeared while tourists were on a boat trip in Brazil.

Holidaymakers were exploring the Lago de Cunia Extractive Reserve in Porto Velho, home to up to 36,000 of the reptiles, when the predators emerged in the muddy water.

Footage captured the visitors screaming as multiple black crocs appeared close to them on October 25.

Over the course of the roughly two-hour journey, the crocs came within metres of the watercraft, often lifting their heads as if watching the travellers.

The route then continued along the Igarape do Campo, a stretch of water famed for its rich wildlife and lush vegetation.

Tour guide and agency owner Jefferson Araujo said the tours are designed to let people safely observe the local fauna.

He added: 'The trips in the Resex are guided by residents who know the behaviour of the animals and understand safe observation distances.

'This community-based approach ensures the safety of visitors and the protection of the environment.'

The black caiman is one of the largest predators in the Amazon rainforest, capable of growing up to 16ft and weighing over 300 kilogrammes.

Native to the Amazon basin, these reptiles primarily feed on fish, birds, and small mammals. Although they are formidable hunters, black caimans are a vital part of the ecosystem, helping maintain the balance of their wetland habitats.

They are generally not aggressive toward humans unless provoked, threatened, or protecting their territory or nests. Most attacks occur when people get too close or disturb them in shallow water.