A surfboard, comprising: a first air chamber (11, 21, 31) and a second air chamber (12, 22, 32); and a partition (13, 23, 33) arranged between the first air chamber (11, 21, 31) and the second air chamber (12, 22, 32), the partition (13, 23, 33) comprising: a first connecting portion connected to a top wall of the first air chamber (11, 21, 31) and to a top wall of the second air chamber (12, 22, 32); the first connecting portion comprising two top wall connecting pieces symmetrically-arranged, each comprising an extension piece extending between the first air chamber and the second air chamber; a second connecting portion connected to a bottom wall of the first air chamber (11, 21, 31) and to a bottom wall of the second air chamber (12, 22, 32); the second connecting portion comprising two bottom wall connecting pieces symmetrically-arranged, each comprising an extension piece extending between the first air chamber (11, 21, 31) and the second air chamber (12, 22, 32); and characterised by an intermediate portion extending between the first connecting portion and the second connecting portion and consisting of only a single, integral piece of material; the intermediate portion defining with the first connecting portion, or with the second connecting portion, a Y shaped portion. a first air chamber (11, 21, 31) and a second air chamber (12, 22, 32); and a partition (13, 23, 33) arranged between the first air chamber (11, 21, 31) and the second air chamber (12, 22, 32), the partition (13, 23, 33) comprising: a first connecting portion connected to a top wall of the first air chamber (11, 21, 31) and to a top wall of the second air chamber (12, 22, 32); the first connecting portion comprising two top wall connecting pieces symmetrically-arranged, each comprising an extension piece extending between the first air chamber and the second air chamber; a second connecting portion connected to a bottom wall of the first air chamber (11, 21, 31) and to a bottom wall of the second air chamber (12, 22, 32); the second connecting portion comprising two bottom wall connecting pieces symmetrically-arranged, each comprising an extension piece extending between the a first connecting portion connected to a top wall of the first air chamber (11, 21, 31) and to a top wall of the second air chamber (12, 22, 32); the first connecting portion comprising two top wall connecting pieces symmetrically-arranged, each comprising an extension piece extending between the first air chamber and the second air chamber; a second connecting portion connected to a bottom wall of the first air chamber (11, 21, 31) and to a bottom wall of the second air chamber (12, 22, 32); the second connecting portion comprising two bottom wall connecting pieces symmetrically-arranged, each comprising an extension piece extending between the first air chamber (11, 21, 31) and the second air chamber (12, 22, 32); and characterised by an intermediate portion extending between the first connecting portion and the second connecting portion and consisting of only a single, integral piece of material; the intermediate portion defining with the first connecting portion, or with the second connecting portion, a Y shaped portion.