The interaction between the two atoms of H in H2 with the lower energy corresponds to a covalent bond between hydrogen's.
When the two atoms of H form a bond, they are overlapping the individual orbitals to form a new one. Every hydrogen has 1 electron which sits in a 1s orbital and then form one molecular orbital. The energy of H2 is lower than individual hydrogens because the electrostatic interaction between them.
Hydrogen is collected by downward displacement of water as it is less denser than water. Hence it comes out at the surface of water . It is insoluble in water so it does not dissolve in water
