A seven-metre long inflatable boat with five Dutch nationals aged between 24 and 48 crashed into rocks at Punta Gavina, Formentera on Thursday morning.
The accident happened at around 3.45 am, killing a male passenger, 35, who suffered a cardiac arrest.
Another man, aged 48, was taken by helicopter to Can Misses hospital in Ibiza after suffering a serious leg injury.
The remainder of the group suffered mild injuries and were treated in Formentera.
The Guardia Civil has opened an investigation into what led to the accident, including what the group were doing on the small craft in the middle of the night.
Authorities quickly pointed out that the first indications were that the boat was not involved in drug trafficking or illegal immigration.