Straightforward but deceptively powerful mono-blueish Otter Prowess Tribal aggro. Although few decks are as explosive as RDW, this one has its definite moments, and feels competitive.

If you want to make the deck real mono-blue just take out the blue-green lands, but you'll miss out on the Elusive Otter's venture spell (unless you luck out with a Mirrex).

Creatures

Elusive Otter - 1 drop with prowess and is unblockable by weaker creatures. It's debatable whether it's worth having taplands for the Adventure side but I prefer it.

Kitsa, Otterball Elite - Great little otter. Most importantly it loots and has vigilance. You can also copy spells for only 2 mana, but there are some relatively easy hurdles to clear to do that. The spell that you're copying will bring you to 2 power, so you only need 1 more, which is either from a counter, a second spell (not likely you'll have all the mana for this), or if you get another Prowess bump from Roaming Throne or Valley Floodcaller.

Valley Floodcaller - The 3 mana may seem steep, but you get an extra prowess for all your creatures from it. Plus the deck is heavy on sorceries, so it gives you some extra flexibility. You can cast it with flash so that helps you cast it when it's more convenient for you, too.

Roaming Throne - 4 mana may seem like a tough sell for an aggro deck, but it doubles all your otter Prowess triggers, which can make things crazy. If you have a Valley Floodcaller and this out, each of your Prowess otters will get +4/+4 from each spell. In this scenario the Throne is 6/6 as well.

Instant/Sorcery

I probably need some 1 drops here but these seem to work. Open to suggestions.

Grove's Bounty - Even when I add some green lands, I find myself rarely casting this Adventure before casting the Otter side. So splashing green lands is debatable. And when I cast it it's often just as a 1 mana Prowess trigger.

Pearl of Wisdom - Obviously this is basically a 2 mana draw 2 considering this is an otter deck.

Otterball Antics - prowess trigger from the spell plus gives you an otter, pretty nice.

Zhalfirin Shapecraft - Nice combat trick that replaces itself with the draw.

Jailbreak Scheme - The only pseudo-removal in the deck, but it also functions as a buff (rarely find myself using).

Enchantments

Stormchaser's Talent - 1 mana otter is a no brainer, plus since it's an enchantment you get a Prowess trigger. Leveling it up is expensive, but this can save the day when a game runs long by letting you get a spell from the graveyard. I almost never hit level 3 with it, though theoretically it's amazing.

Lands

All the rest of the lands are obvious, but I have to say this about Three Tree City. Even in a tribal deck like this, it's not that great. It only breaks even with other lands when you have 3 creatures of the same type. It's probably better in non-aggro decks, but considering this deck usually wins before the 4th creature gets out, it's not that great. But it's also unlikely that it will hurt you because you'll usually have other lands for colored mana.

Maybeboard -

The Enigma Jewel // Locus of Enlightenment - I've been playing with 1 of this to activate the Talent levels and for Kitsa. It kind of feels bad drawing it since it's just a helper, but it's only 1 mana, it triggers Prowess, it helps you cast Kitsa spell copies for free, and makes leveling the Talent much less daunting.