burst forth, rise, vigorous
浡 centers on a sudden, forceful emergence: water bursting forth, rising up, or showing vigorous energy.
浡 combines 氵 (water) with 孛, which likely contributes the sound and the idea of sudden growth or bursting. The exact historical development of 孛 is uncertain.
Water 氵 plus the bursting shape 孛: imagine a geyser of water suddenly bursting forth from the ground with vigorous force.
For ホツ, picture a hot spring suddenly bursting forth: hot -> ホツ, and the water rises vigorously.