The whales aren't migrating when in Samana Bay during the winter. They are mating and giving birth.
Punta Balandra in Samana is a place where you can often observe whales without going out in a boat.
If you decide to go out in a boat, go with Kim Beddall, the founder of whale watching in Samana. She has had a lot to do with getting all the other boat operators to respect the whales they are taking people to observe.
http://www.whalesamana.com/