I like to look at GFI's yearly state of alternative seafood reports [1] to get a sense of the landscape. New harvest has a good list of research they have funded which gets into the weeds a bit [2], check this one for example [3]. We wrote some pros and cons in my recent article that may be interesting [4].
This is a list of some players: Finless Foods, BlueNalu, Wildtype, Shiok Meats, Bluu Seafood. Most are at the pilot plant stage and have announced reaching market this or next year. Note that the investment landscape have changed dramatically last year, so timelines will likely change.
Finally: I think its going to be exciting to see alternatives coming out soon. For me the pros are definitely welfare and biodiversity related, while the cons are feed and co2 related.
1: https://gfi.org/resource/alternative-seafood-state-of-the-in... 2: https://new-harvest.org/publications/ 3: https://www.frontiersin.org/articles/10.3389/fsufs.2019.0004... 4: https://www.sciencedirect.com/science/article/pii/S0308597X2...