Surf Legend Laird Hamilton -- Don't Poo In the Ocean ... It Attracts Sharks!

Great brown could lead to Great White ... so says surf legend Laird Hamilton who tells TMZ Sports he has a strict NO AQUAPOO policy ... because sharks could be drawn to log fish.

Bottom line ... when nature calls, Hamilton says he'll clench up and paddle in because "I just feel like I might be calling something on that I probably don't want to come ... sharks."