Figures with the dolphin symbol....well my question is what exactly can they do? can they move faster in water? And is water considered hindering terrain???

Water is considered a special hindering terrain. And yes, they move differently in water; aquatic figs are not stopped by walking into water terrain and can move their normal movement value through it (yay atlantis rising).

From the Marvel Universe Rule Book (page 19);
Water: Shallow water features, such as streams and ponds, are hindering terrain for movement, but not for line of fire purposes. Characters that can swim (that have the dolphin symbol on their base) treat water terrain as clear terrain for movement purposes.

All Dolphin movement does for you is allow you to ignore water terrain for movement. Oh, and also use that Infiltrate Feat coming out in Icons.

I think you meant the "Submerged" feat, right?

It allows you to use either feat.

Yeah I guess it helps if I read the WHOLE card! I was happy after the first half! LOL