Horsea is card #49 of 95 in HS—Unleashed (2010), a Common illustrated by Shin Nagasawa. At about $4.36 it is the #69 most valuable card in the set. In a HS—Unleashed booster it turns up about once every 5 packs. It is one of 28 Horsea cards printed so far.
1999Fossil
2003Aquapolis
2006Holon Phantoms
2010HS—Unleashed
2015Primal Clash
2018Dragon Majesty
2022Lost Origin
2024Shrouded Fable

















See the full HS—Unleashed card list
An ungraded Horsea from HS—Unleashed sells for about $4.36. A PSA 10 is worth more, roughly $34.88 by our estimate, and a PSA 9 around $12.21.
It is a Common, and it shows up about once every 5 HS—Unleashed packs.
Shin Nagasawa drew the art for this card.
Yes, as a digital simulator. Holobrook lets you open HS—Unleashed booster packs in your browser with the set's real pull rates and keep what you pull in a digital binder. No real cards, nothing to buy.