Total Solar Eclipse of 2021 December 4
 in Antarctica from the icecap, an eclipse flight or cruise

Realistically speaking, eclipse observations from a cruise ship are only likely in the portion of the eclipse path between the South Orkney Islands and South Georgia Islands, that is known as the Scotia Sea. While some cruise companies advertise Weddell Sea destinations, these expeditions can only go to the eastern side of the Antarctic Peninsula, which lies outside the path of totality. In the Weddell Sea, ice conditions are too heavy in early December to allow anything but the largest icebreakers to reach the edge of the Filchner-Ronne Ice Shelf where the point of greatest eclipse is located. The Weddell Sea pack ice is not meant for regular Antarctic cruise ships, which means that those ships can not and will not go farther south than about 60 degrees South. To intercept the total solar eclipse track they’ll be limited to the edge of the Scotia Sea drift ice. Moreover none of those cruises will cross the Antarctic circle where the Sun never sets for six months. The only icebreaker that could deliver is likely the Russian Kapitan Klebnikov which was used previously in November 2013.
While the average cloud cover map in December shows rather pessimistic conditions for the month, day to day satellite images are slightly more optimistic. With enough mobility and time, there are sometimes large areas with open or nearly open skies beneath the eclipse track that a ship can reach. That said, considering the Sun is fairly low above the horizon, finding the best possible viewing area may prove difficult to achieve even with modern means, state-of-the-art technology, and is likely to come at the expense of a reduced totality duration and eventually some rougher sea with wave heights of about two meters. Their best chance is likely to take advantage of the lee side clearing that typically comes with flow over the higher terrain of the South Orkney Islands, that is usually the northeastern side as prevailing winds are from the west. The price to pay being to loose about 40 seconds of totality and get only about one minute.
Using an operator allowing enough time in the expedition schedule to maximise the chances of finding a break in the weather if the path of totality experiences cloudy weather is paramount to success.

Here is a cruise I can recommend, with a brand new ship having a good speed.