Heat water, onion, butter, curry powder, and salt in a large skillet over medium heat until butter is melted, about 2 minutes. Stir rice into onion mixture and arrange frozen white fish over rice. Sprinkle with almonds.

Reduce heat to medium-low, cover, and simmer until the rice is tender and the liquid has been absorbed, about 20 minutes. Fish should be heated through, and the flesh should be opaque and flake easily. Mix in peas and fluff rice with a fork before serving.