What is involved in raising a shipwreck from the bottom?

To answer your question depends on the type of wreck. The size of the wreck. Condition of the wreck. Location and depth of the wreck and equipment required. An old wooden wreck that has been on the bottom for a while might break apart when it is salvaged. It would have to be underslung and lifted into an underwater metal sling and then everything lifted at once. In Lake Ontario there are two 1812 wrecks that are not big. It would cost millions to raise them. Then there is the problem with salvage rights. Insurance companies still own the wreck and governments have laws to keep people from salvaging wrecks. A small wreck like a fishing boat would cost in the 10's of thousands. A larger vessel might run into the hundreds of thousands if not millions.