[AFreeBird]

No supposedly about it. Water doesn’t compress. explode a big enough bomb underneath a boat, especially in shallow water like a harbor, you’ll break the boat’s back.

[Scrambler Bob]

explode a big enough bomb underneath a boat,
= = =

Really doesn’t have to be a big charge, if placed in the optimum region.

[pierrem15]

I would think the pressure wave dissipates in proportion to Pi*r^2 from the center of the explosion.

If the blast generated 100 lbs/sq. inch of over pressure at 10 ft, then at 20 ft (double the distance) = 100 / 3.14*4 = 7.96 lbs / sq inch.

That's why ship mines have 1000+ lbs of TNT, although we tend to forget even 5lbs of over pressure will generate 18,000 lbs of force on a 5'x5' hull plate, probably more than enough to rip the welds at some points.