Which way is considred returning from sea on the ottawa river ?

Question

which way is considered returning from sea towards georgian bay north or towards the north atlantic south ?

Answer 1

The ottawa river flows into the St Lawrence and then out to the Atlantic ocean.

Going up the river to its source you are travelling AWAY from the sea.  Following the river down TO the sea is going toward the ocean.

Answer 2

If you are returning from the sea, on the Ottawa River you would generally be heading north (or northwest).