I don't think the wilderness/water decision is as simple as you imply. The "woods" closest to NYC would be a nightmare. Those in Newfoundland would be no more crowded than before SHTF. The water closest to NYC would be a nightmare. The waters off Newfoundland would be no more crowded than before SHTF. It would be hard for a particular pirate to find one boat on the open ocean, but multiple pirates will trip over multiple sailors, especially within thirty miles of major ports, and it's hard to outrun someone built for speed if you're built for comfort and on a budget. Unless you really are far from land (transit to/from Guam), which would make many marginal sailors squeamish, I don't think either land or water is an obviously superior choice.
I'm not disagreeing with your fundamental point, that for perhaps 3% of people, sailing is a great SHTF plan. I'm just saying that the choice requires balancing several factors.
Hey, if you can live in Newfoundland, great. I couldn’t.