Fr Simon Henry's blog, it is a Russian Bishop taking part in the Epiphany Baptismal rites, in which Orthodox renew their baptism in remembrance of Christ's glory being shown forth at his baptism.
In many places where Holy Communion is rarely received or even attendance at Sunday Liturgy is lacking this "renewal" becomes an annual marker of being Orthodox. In some parts in is a pleasant dip or sprinkling in Russia a rather fearsome an act of asceticism, reminiscent of the martyrs of Sebaste who were left to perish on a frozen lake. There are more photograph's here.
There is something manly about plunging into an icy pool in the middle of winter, I have been trying to think of Western parallels, apart from rigourous Lenten fasting or all night vigils, I can only think of St Patrick's Purgatory in Ireland or the blood and chains of certain unreformed remote Spanish or Italian Holy Week celebrations.
Coptic Orthodox men in Brighton seem to love to shame me by telling me of the vast numbers of fast days in their calendar and Muslims of their Ramadam austerities, there seems to be something about austerity, even physical pain that is attractive to men in the service of God.