This is a discussion on Unusual carry scenario - need advice on deep concealment holster within the Defensive Carry Holsters & Carry Options forums, part of the Defensive Carry Discussions category; steve...
Concealment vest (type with holster pocket built in) might blend in well among the fishing crowd.
Survival Sheath makes a chest option, which could work depending on your type of shirt.
Safepacker might also work, or a fanny pack (esp. the Camelbak fanny or backpacks).
Belly band, possibly?