why does a wood boat sink to the bottom when filled with water I mean the average density of the wood and the water should be less than that of water so by my reasoning it should float just below the surface but it doesn't any explanation

punctuation is your friend.

In the case of the older ships from the days when sail was king, several reasons come to mind...

1) Metal fittings on the ship
2) Stone ballast in the bottom of the ships hull, sometimes quite a few tonnes
3) cargo, in the cases of many ships may have been gold or silver. (There were three Spanish Galleons that were noted as having been loaded to theier sailable capacity that went down off the coast of Florida in the 1500's. Recently they were discovered)
4) Cannons and cannon balls. Maybe even the gun powder once it got wet.


Probably a vast number of other things conspired with the above mentioned to help drag the vessal down.

Even a rowing boat with no cargo or anything made out of wood still sinks

air keeps it afloat, water sinks her.

~Thanato

A row boat sinks because the wood becomes saturated with water. Much like a tree linb that falls i a pond will sink after it becomes "water logged". That's one of the reasons for painting a oat with water-proof paint.

Wood is after all a solid and if all the microscopic voids in the wood were removed, (maybe by compacting it under a great deal of pressure), it would sink like a rock. With a wooden row boat, once those tiny voids in the wood become full of water they no longer provide buoyancy. The boat would then be perfectly neutral except for the fact that the wood itself has weight. The weight of the wood will then allow the boat to sink.
Think of a metal bucket. It will float because of the void inside of it. If that void is filled with water it will sink because the metal weighs more than the water around it. A zepplin will float in the air as long as it's filled with something that weighs less than the air around it. Fillit with regular air and it will drop like a rock.
The same thing applies to a boat made of wood.