For freshwater, you just need to purchase a freshwater guide license (Texas resident) #600 for $132.
For saltwater, you do not need a USCG OUVP license. You are required to have an all-water paddle craft license (Resident of Texas) #650 for $210 and additional items as listed below..https://tpwd.texas.gov/publications/pwdpubs/media/pwd_bk_v3400_0074.pdf
All-Water Paddle Craft
Resident (Type 650).................. $210
Non-resident (Type 750).............$1,050
Required of any person operating as a fishing guide and utilizing paddle craft (canoes, kayaks, etc.) in all coastal waters. NOTE: Persons operating as a fishing guide and utilizing paddle craft (canoes, kayaks, etc.) while guiding can qualify for a fishing guide license upon presentation to a license agent of certification or proof of completion of a TPWD boater safety course, CPR/First Aid training, and completion of the American Canoe Association Coastal Kayak Day Trip Leading Assessment or the British Canoe Union Four Star Leader Sea Kayak Certification. This license is applicable only to paddle craft and cannot be used when a person is operating a motorized vessel.
Any person who possesses an All-Water fishing guide license and a valid USCG vessel operator’s license is qualified as an All-Water paddle craft fishing guide.
All-Water fishing guide and All-Water paddle craft licenses available only at TPWD Law Enforcement offices. Freshwater fishing guide licenses available at any location where licenses are sold.