I've always fancied the concept of "A Very Canadian Response".
Stealthy subsurface vehicle stealthily transiting Canadian waters.
Stealthy vehicle detected by Canadian sensors.
Canadian asset deploys submunition.
Submunition swims stealthily to stealthy subsurface vehicle and stealthily attaches itself to the hull with a limpet mine style magnet.
Submunition announces itself with three sharp taps.
Knock, knock, knock.
"Greetings and welcome to Canada. Bienvenue au Canada. We are pleased that you have chosen our waters for your current voyage. We request that you kindly report to the nearest Customs Port and declare yourself. For your convenience Customs Ports are located at the following locations: .... alternately you may declare yourself to any of our roving Customs Officers located on Her Majesty's Canadian Ships. They will be happy to accept your declaration. Nominal service charges will apply. Visa and Mastercard only are accepted. We wish you a safe trip. Bon Voyage."
Limpet submunition then starts broadcasting a very noisy and annoying ping pattern.