Truly waterproof glue and waterproof finish

I am probably daft for even considering it, but I am thinking of 
building a wooden bird bath to stand permanently in my garden.  Can 
anyone tell me if there is a glue out there that will stand being 
constantly immersed in water and is there a finish that will waterproof 
and preserve the timber without poisoning the birds or tainting the water?

While I have your attention any suggestions as to the timber?

Gary(UK)