A splashdown in the ocean used to mark the end of an astronaut's mission. For ESA astronaut Timothy Peake and his crewmates, their mission will have just started. Today, some time during 11:00-13:00 GMT, Tim will dive to an underwater base off the coast of Florida. Neemo missions train astronauts for life in space. Living and working in an underwater base is similar to space stations.

During the 10-day mission, Tim and his six crewmates will live in cramped conditions, perform 'waterwalks' and will have to solve problems as a team.

The base is around 20 m under the sea and aquanauts will experience air pressure 2.5 times than at sea level.

At this depth, the aquanauts will not be able to surface without safety stops. Quick evacuation to fresh air is not possible.

This year Neemo aquanauts are challenging students to prove their understanding of natural phenomena in an educational programme called Science Under Pressure.

Tim and fellow aquanauts performed a number of educational experiments before diving down to the Neemo base. What will happen when the same experiment is performed under pressure? Will fizzy drinks still have their bubbles? Will toy helicopters be able to fly in the denser air of the underwater base?

Students are invited to follow the Neemo mission and speculate on the outcome of these experiments. The first correct answers on Facebook and Twitter will receive official recognition.

Follow Neemo via social media. In addition to the specific Neemo Facebook and Twitter accounts, Tim can send tweets via @Astro_TimPeake. ESA's astronaut trainers will be blogging and tweeting on ESA's astronaut blog and via @Astro_trainer.