plomp

There was a "plomp" as it reached the water, a bubble or two came to the surface, and all was over.

Many Cargoes 1903

And whan thei wil fighte, thei wille schokken hem to gidre in a plomp; that zif there be 20000 men, men schalle not wenen, that there be scant

The Voyages and Travels of Sir John Mandeville 2004

And whan thei wil fighte, thei wille schokken hem to gidre in a plomp; that zif there be 20000 men, men schalle not wenen, that there be scant

The Principal Navigations, Voyages, Traffiques and Discoveries of the English Nation 2003

"My friend, sir," the second man went on, "is vat you call chippy because you come plomp into his bed of cabbage, very fine vegetable, vich remind him of his youthful days in ze ever-to-beloved Homeland."

Round the World in Seven Days Herbert Strang

Then he flings it recklessly high in air and you hear it fall (the big drum does this) with a loud plomp in the road.

The Harlequinade An Excursion Harley Granville-Barker 1911