I'm happy with that. Next?
Updating
Merhorse Working Draft.
It's still missing a description, and we could do with a few lines about the Long-Necked.
How about.
Driving through the water is the horselike head of a creature with a striking red mane. Its only limbs are a pair of flippers at the front of its long, slim body. The mane runs down its neck to merge into a rough crest along its back that ends near the base of its two-lobed tail. The sea beast's face has enormous dark eyes and a wide, pale-lipped mouth edged with bristles.
Dang it, while writing the above I noticed the bit about them having oversized eyes, suggesting good vision in the dark depths of the sea.
I guess we should either increase the Listen/Spot ratio of the skills or give it a racial bonus to Spot checks. I'm leaning towards a bit of both - maybe switch the odd point into Spot and add a +4 racial bonus? We can give the Long-Necked the Listen +12/Spot +11 version, as it's got small eyes.
Merhorse Revision:
Skills: Listen +11, Spot +16, Swim +21
Skills: A merhorse has a +4 racial bonus on Spot checks. A merhorse has a +8 racial bonus on any Swim check to perform a special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.
For the Long-Necked:
Long-Necked
A sea beast with a tiny round head upon a very long neck. Its long, sausage-like body bends into humps as it swims along. The creature has a pair of stubby hornlike tubes atop its head.
The long-necked "sea serpent" is another giant aquatic mammal that is likely to be descended from seals. It has the same statistics as a merhorse except for the changes given below.
A long-necked's bite attack is treated as a secondary attack that adds only half the long-necked’s Strength bonus to damage. A diving long-necked cannot hold its breath for as long as a merhorse since it lacks the merhorse's oxygen-absorbing mane, but its "horns" are snorkels that allow it to breathe while barely breaking the surface of the water.
Attack: Bite +13 melee (1d8+5)
Skills: Hide –12* (+13 when snorkeling), Listen +12, Spot +11, Swim +21
Challenge Rating: 5
Hold Breath (Ex): A long-necked can hold its breath for a number of rounds equal to 6 × its Constitution score before it risks drowning. For a typical long-necked, this is 84 rounds, or over 8 minutes.
Skills: A long-necked has a +8 racial bonus on any Swim check to perform a special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.
*A long-necked can lie in the water with only the tip of its horns showing, gaining a +25 cover bonus on Hide checks.
