The tactics below should only be attempted by experienced snorkelers or certified scuba divers.

Legal options:

If you have taken a dive class, you already know that when you are diving near your dive flag, boats must typically stay 100-200 feet away from you and your dive buoy, depending on local laws.  If a few divers were in the water, spaced evenly across the starting point of a fishing tournament, how can the event legally proceed? We do not typically expect fisherman to follow laws, if employing this tactic make sure you have someone near by that can document their violations.

A small length of PVC or metal pipe makes a hell of a racket underwater and can easily drive fish to another area.  Note: Sudden loud underwater noise will stun fish; use care.