The Sea Bird is an old (built 1981), small (62-passenger), quite basic expedition ship with little pretense of decor and the most cramped cabins I have ever seen. (The best bets are cabins 106, 214, and 217.) It bounces sickeningly in rough seas, which are fortunately rare in these waters. The cuisine is adequate (good dessert chef).
This ship is desirable only for its itineraries. You can see Alaska's inside passage very well on more comfortable ships--think Silversea--but if you want to see the great whales of Baja, you have no better choice than Sea Bird. It's a 7-day trip--you fly in and out of La Paz, busing across the peninsula (about a 3-hour drive) either at the start or the end.
On our trip, the bus ride was at the start, and we boarded at Puerto San Carlos (which is not the San Carlos farther north in Baja) on the Pacific. In narrow Magdalena Bay, setting out from the ship on Zodiacs, we had many close and exciting encounters with gray whales, usually cows traveling with their calves. We had a day and a half of these adventures. Then we set out for Cabo San Lucas, rounded Land's End, had a port stop in San Juan del Cabo (nice walk in a bird sanctuary), and continued up into the Sea of Cortez. Here humpback whales are the main objective. There seemed to be fewer of them, spread across a great expanse of water, but they display a wider variety of behavior than the grey whales and were very enjoyable to watch during our relatively few close encounters.
We saw no other species of whales. But we had a delightful extended encounter with a superpod of hundreds of dolphins, detachments of which often leapt in unison. We saw many rays that leapt so high above the water that they performed several flips before re-entering. And at one rocky islet our Zodiacs were closely followed by swarms of California sea lions, among whom we also had the opportunity to snorkel. Throughout, the commentary of the on-board naturalists was interesting and valuable.
You're on the Sea Bird in the waters of Baja to see marine mammals, and you certainly do, better perhaps than anywhere else in the world. Opportunities to do this don't fill your seven days, which also incorporate some inevitable padding. But for those not distressed by a total dearth of luxe, the Sea Bird is your best passage to an experience very much worth having.