This is the 17014th most frequent Russian word.
спасательным
"Rescue" or "lifesaving" (adjective).
In this sentence, "спасательным" describes the purpose of the ring as meant for rescue purposes, functioning as an adjective in a descriptive phrase.
Мы увидели спасательным кружком на берегу моря.
We saw a rescue ring by the sea shore.
In this instance, "спасательным" is used to specify the vehicle's primary function related to rescue activities.
Они приехали на место происшествия на спасательным транспортом.
They arrived at the scene in a rescue vehicle.
Here, "спасательным" describes the type of equipment used for rescue operations, indicating its functional attribute.