Normally wood log must be floating on the water but ?

The original diety of Kancheepuram Varadaraja Swamy Perumal is made out of Athhi Maram or the fig trunk and that seems to be stronger and longer lasting than any other wood. As a layman, I am having a big doubt as to a wooden log when thrown on the water it must be floating and won't sink but in this case, the diety would be drowned inside the temple tank and won't be taken out for next 40 years. How come a wooden log can stay inside. Technical answer from the experts of this site greatly solicited.