The international crew of a fishing boat that sank off the south-west coast of Ireland could not speak a common language, accident investigators have said today.

Communication was so difficult between the 18 people on board the 36-metre Royalist, which got into problems off An Daingean, Co Kerry, in January that sign language had to be used.

Even the skipper could not understand safety and risk notices which were written in English and Spanish on the UK-registered boat.

The UK's Marine Accident Investigation Branch said a weather-tight door between the main working deck and an alley that was left open in rough seas was key to the sinking.

There was a notice in English warning crew to ensure the door remained shut when at sea.

All 18 crew were rescued by a French fishing boat which headed for the scene when it heard a distress signal.

While the skipper and seven others were Portuguese, eight deck hands and an engine room operative were Indonesian, the cook was Spanish and the engineer was Peruvian.

'The Portuguese nationals could generally communicate with the cook and engineer, but communication with the Indonesian crew was more difficult and was limited to an exchange of very basic Spanish words,' UK's MAIB report said.

'None of the crew could understand or speak English and the skipper's knowledge of Spanish was very limited.'

The boat's risk assessments were written in Spanish and could not be understood by all the crew, including the skipper, according to the MAIB investigation.

It also said that the make-up of the nationality of the crew was against its licence regulations, which requires 75% of those onboard to be EU nationals.

The Royalist sank after it was struck by two huge waves.