The Spanish Navy pledged support to Monturiol but did not actually supply it, so he had to raise funds himself, writing a letter to the nation to encourage a popular subscription which raised 300,000 pesetas from citizens of Spain and was used to form the company La Navegación Submarina to develop the Ictíneo II.

The Ictíneo II made her maiden voyage under human power on 20 May 1865, submerging to 27.5 metres (90 ft).

To this end he invented an air independent engine, which ran on a chemical reaction fueled by peroxide[2] that provided its own oxygen for combustion.

However, due to the state of his finances, construction of a new vessel was out of the question, and instead he managed to assemble enough funds to fit the engine into the Ictíneo II.

Two months later, on 14 December, Monturiol submerged the vessel and ran his chemical engine, but with a quite slow speed of 2.5 knots (4.6 km/h).

The chief creditor called in his debt, and Monturiol was forced to surrender the Ictíneo II, which was his sole asset.