When Vaanar have known about Seetaa's whereabouts through Sampaati, they all started thinking as who could cross 100-Yojan wide sea to see Seetaa. At that time..

Here (in both Maanas and Raamaayan) Hanumaan is said to be sitting 'comfortably' far from the madding crowd of monkeys. When everybody is clamorous how can this monkey sit comfortably - clearly creates the doubt. In reply it may be said, that he is apparently comfortable but in his heart of hearts he is churning the problem of vaulting over the ocean and if so, then who is to go. 

On one hand, Raam gave his golden ring to Hanumaan in the presence of these very same monkey heroes, and on the other hand Angad is asking all the monkeys to jump over the ocean. Hanumaan is fully aware that all the other monkeys are somehow escaping the situation, not because they cannot jump just a 100-Yojan ocean, but owing to the fear of Raavan. 

Hanumaan neither fears Raavan nor cares the stooge-Raakshas, but his concern is his duty. If somebody comes forward to leap, then it is well and good and Hanumaan has to accompany that monkey as a standby, because he is handling the ring of Raam. If none comes forward, even in that event he has go to Lankaa unaccompanied, alone. In either case it is Hanumaan who has to go, hence the 'comfortableness' is 'decisiveness' and thus he is deciding his duty.

A verse from Skand Puraan says this only: 

neelo angado hanumaan cha jaambavaan ath kesaree | 
samudra teeram agamya na shekuh spanditam padam | 
raavanasya balam gyaatwa teerey nada nadee pateh || 
-- Skand Puraan

[From - Valmiki Ramayan 4/65/35]