The Dutchman, who was linked with a St James' Park exit, has seen Mathieu Debuchy, Mapou Yanga-Mbiwa, Yoan Gouffran, Massadio Haidara and Moussa Sissoko arrive.
And Krul now hopes Newcastle's new French foreign legion can help in the fight to beat the drop, starting with Tuesday's six-pointer against fellow strugglers Aston Villa.
Krul said: "The owner (Mike Ashley) and chairman (Derek Llambias) did what they said they were going to do. Five new players is more than I expected.
"It's given everyone a massive lift. The club said we were going to strengthen the squad and they showed that in five or six days, signing five new players.
"It gives that extra competition for places, instead of taking things for granted and people will have to work their socks off to stay in the side.
"At a club like Newcastle, you need that. Before now with the injuries we had we were just happy to get 11 on the pitch and a bench. We've definitely got strength in depth now."
But relegation is still a major worry for Newcastle, who, in the wake of last season's excellent fifth place finish, currently find themselves just two points above the relegation zone.
Krul sees similarities to Newcastle's relegation in 2009 when they were sent down at Villa having previously been considered too good to be relegated.
He said: "Everyone said we were too big to be in this fight but we're not. We're in it and we have to get out of it as quickly as possible. We can't take things for granted like we did then."
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