The underside of the bell is partially constricted by a velarium,[2] a horizontal ring of tissue,[3] and in the centre is a manubrium, a tube-like structure which hangs down with the mouth at its tip.

[2] The World Register of Marine Species lists the Caribbean Sea and the Central Indo-Pacific as habitats, but marks them as unreviewed.

[6] During the day Tripedalia cystophora is mostly to be found within 20 cm (8 in) of the surface, in sunlit positions among the prop roots of mangroves.

These warm sunlit areas are where its main food item, the copepod Dioithona oculata, are to be found during the day.

[5] Dense swarms of these copepods form in the illuminated patches of water where shafts of sunlight shine through the mangrove canopy.

It has been found that Tripedalia cystophora displays complex behaviours such as the avoidance of obstacles and fast swimming in a particular direction and is able to maintain its position in the shaft of sunlit water presumably by using visual cues.

[2] It is later expelled and settles to the bottom where it undergoes metamorphosis into a polyp about 1 mm (0.04 in) long with four, knob-tipped tentacles surrounding a mouth.