I agree with that. Quick fine - on the spot - which the agency would work with the charter company to enforce as well. No requirement to move if after sunset or close to sunset. Random swing past in the day to ensure the 90 min limit is enforced. Would generate decent income for the treasury, for a short period of time till the charter companies spread the word about how serious the agency is.

Same applies to charter boats taking up the commercial dive boat moorings as well... I have seen arguments develop between commercial dive boats and charter boat crews, bringing a paying group to dive a site, only to see a big cat sitting at the dive boat mooring with no plan to move on.

Sometimes people forget the fact that need to pay attention to customs and rules, even if it gets in the way of their holiday plan!