While there may some risk of introducing pollutants to tank if gathered right near shore...they are probably negligible compared the "legal" and "moral" risks.
Check out "rules" closely.
You did not mention water, which I think would great if you could get a good ways off shore. (Maybe use a UV sterilizer on it just to be safe.)
I think in general, if you are not a licensed collector, not a good idea.
"Om" 
"Reef on"