10MT Nuclear Explosion at 100ft Burst depth (Patreon)

A 10 MT explosion near the surface will create a "Wave Train" over 100 feet in height within 6nm.  Source: Water Waves Generated by Underwater Explosions Feb. 1996

As the wave approaches shore, the speed goes down and wave height increases. Source: Australian Government Bureau of Meteorology; Facts and Information page

The T-15 Torpedo was a 40MT nuclear device.