Unfortunately I'm too far north for cypress trees. but pine is common around here. The biggest problem for me is figuring out how to move a log that size back to my house. I had a great idea for a cheap sealant when the boat is finished. Cooking Oil!!! I'm going to buy a few big jugs of it and paint it on with a brush.
The cooking oil will likely go rancid and start to smell quite bad. Makes a very good bait for bears however!
I'm not sure if you have a problem with bears where you are, but I've seen them rip the boards off of a wood shed wall to get the used cooking oil inside.( city man moved to the country,neighbour of my folks). I'm just passing on some info , of course .
I've also seen where holes were drilled from the outside after it was shaped. The holes were small 3/8" or smaller ,strategically placed and they were plugged with coloured pegs of precisely the length that corresponded with the wall thickness desired,+ a little for finish shaping. Something like walnut would contrast well with pine. When you are shaping the inside , and come to the peg, you know exactly how thick the wood is. Make sure you keep it in the shade to slow the drying. Cracking will be your worst enemy. Seal the ends right away.
Good luck with the canoe.!