We completely forbid the use of long fins...
Marcus - Instructor/Dive Center/Dive Boat Owner
March 19, 2005 at 00:12:39
We also forbid the use of long fins in both scuba diving courses and on our boat diving trips. Most dive center training revolves around entry-level courses and in that case, long fins are potentially hazardous to the user and other students in the course.
On our boat diving trips, it's strictly an environmental issue. We have enough trouble with diver impact on fragile reefs with standard scuba configurations. Long fins dramatically increase the damage.
Of course, people who use them deny it but we've been in the real-world laboratory for years and the jury is in. Long fins and scuba don't mix. For free diving and snorkeling, it's pretty much a non-issue.
To summarize, it's a safety issue in training situations and an environmental issue in fun diving situations.