We have friends who take these trips regularly. They are inexpensive compared to regular cruises (generally 1/2 the price), the ships tend not to be full, and the ports of call can be interesting.
Many cool choices here: Holland America “Repositioning Cruises”
If you like oceans (and missed service in the Navy), the transatlantic trips are wonderful and relaxing. Lots to see on the Atlantic ocean, and amazing food.