Well, i have a short litte speculation. Do you guys remember those 3 mysterious giant shadows at the Florian Triangle? Well I believe I know what they are inspired of!
Florian Triangle Shadow Monsters
We know Oda like puns and spelling tricks: IMU is UMI backwards, it’s not necessary but why not? Furthermore Kanji for 海, umi means Sea or Ocean, the Kanji 坊主, bōzu means buddhist monk. And when we all know how Imu-sama looks! He looks somehow like a priest, monk with his long robe and pope like crown.
Could it be that those Shadows from the Florian Triangle are Imu or some Creatures that Imu controls to look at Luffy?
Here are some Artworks from Umibozu:
Imu-sama is inspired by Umibozu. Imu-sama is the Ocean Devil/God.
*Theory by Saikō no Kenshi