daplu -plu- gismu

x1 is an island/atoll/key of [material/properties] x2 in surroundings/body x3; x1 is insular.

See also lalxu, rirxe, xamsi, dirgo.

In notes:

dirgo
x1 is a drop [small, cohesive shape] of material [liquid/vapor] x2 in surrounding material x3.
lalxu
x1 is a lake/lagoon/pool at site/within land mass x2.
polno
x1 reflects Polynesian/Oceanian (geographic region) culture/nationality/languages in aspect x2.
ponjo
x1 reflects Japanese culture/nationality/language in aspect x2.
rirxe
x1 is a river of land mass x2, draining watershed x3 into x4/terminating at x4.
xamsi
x1 is a sea/ocean/gulf/[atmosphere] of planet x2, of fluid x3; (adjective:) x1 is marine.
fluplu
x1 is a floating island of material/properties x2 floating on x3.
pevyplu
x1 is like an island in a sea of x2; x1 is very distinct/foreign (in appearance, composition and/or behavior) from surroundings/environment/background x2.