The phrase "veritable sea" means a large and overwhelming amount or quantity of something. It implies that there is an immense expanse, like a sea, filled with a particular thing or things. Full definition
It's certainly not easy for an Italian eatery to carve out a niche among a veritable sea of other Italian restaurants, but this Civico 1845 has done quite successfully. (fb101.com)
A veritable sea of sheepskin and denim - clad skinheads turned the air blue, The atmosphere was on the turn. (goonerholic.com)
The measurements of these lost fast ions also allow for the conclusive identification of the path the particles took en route to the detector, thereby determining which waves (amongst a veritable sea of many different waves) the particles interacted with along their way to the reactor wall. (sciencedaily.com)