Snake pipefish

It will come as no surprise that the long and slender Entelurus aequoreus uses seaweed to hide.

An ambush hunter, E. aequoreus uses its long snout to suck up prey like small crustaceans and fish larvae.

This pipefish breeds mid-summer, and the 1000+ eggs that the female produces are attached to a groove on the belly of the male, who broods them until they hatch.

Source 1: https://www.macduff-aquarium.org.uk/explore/fish-finder/snake-pipefish
Source 2: https://en.wikipedia.org/wiki/Snake_pipefish