Depending on what you’re looking for, Ever will take you for a day of fishing, snorkeling and sightseeing, Gerardo will take you on an eco tour more inclined to the biodiversity of the area, he’s a wealth of information, but I don’t think he’s offering fishing(?).
Ever is located on the north end of the beach, near IMIX. Gerardo is in the center of town near the whale tail, look for the Eco Tour signs.
If you want more serious fishing, further off shore, Team Tex-Mex out of Barra de Navidad has a brand new 31’ boat with all the gear that will get you out there fast. You can find them on instagram @teamtexmex (owned by a local resident of La Manzanilla).