Lobelia is a good guess. Although the leaf shape looks somewhat different, my Lobelia looked similar to that when I first got it. Be patient with it as it adapts to being submerged. I bought 2 of them and one disintegrated. The other grew very slowly at first. Perhaps it was shaded too much
The link kveeti provided lists it as difficult. I have had more difficult plants than this however. It does OK in my tank with 3 wpg, which isn't really "high" light. After a time it may develop a tangled series of roots that extend down from the stem, which can look quite sharp, IMO.
Any good suggestions for a broadleaf plant that won't get to big? I have them in the right front corner of my tank and it has dwarf sag to the left of it. A bit of color would be nice but not necessary...