if CLIENT then

    local blur = Material("pp/blurscreen")
    local emitter = ParticleEmitter(Vector(0,0,0))

    local function emmit_bubbles(ent)

        if ent:BoundingRadius() < 10 then return end

        local vel = ent:GetVelocity()
        local len = vel:Length()
        if len < 100  then return end

        local min, max = ent:OBBMins(), ent:OBBMaxs()

        local pos = Vector(math.Rand(min.x, max.x), math.Rand(min.y, max.y), math.Rand(min.z, max.z))

        for i = 1, 10 do

            local particle = emitter:Add("effects/bubble", ent:GetPos() + pos)

            particle:SetColor(255, 255, 255, 255)
            particle:SetVelocity((vel / 4) + VectorRand() * 10)

            local size = math.Rand(0.25, 3)

            particle:SetDieTime(size)
            particle:SetLifeTime(0)

            particle:SetStartSize(0)
            particle:SetEndSize(size * math.Rand(1, 2))

            particle:SetStartAlpha(255)
            particle:SetEndAlpha(0)
            particle:SetGravity(Vector(math.Rand(-4, 4),math.Rand(-4, 4), size * math.Rand(10, 25)))
            particle:SetCollide(true)
            particle:SetRollDelta(1)
        end

        ent:EmitSound(("ambient/water/wave%i.wav"):format(math.random(1, 6)), 100, math.random(200, 230))
    end

    hook.Add("RenderScreenspaceEffects", "water", function()
        local ply = LocalPlayer()

        if not ply:IsFlying() or ply ~= me then
            if ply.water_snd then ply.water_snd:Stop() ply.water_snd = nil ply:SetDSP(0) end
        return end

        if not ply.water_snd then
            ply.water_snd = CreateSound(ply, "ambient/water/underwater.wav")
        elseif not ply.water_snd:IsPlaying() then
            ply.water_snd = nil
        end

        for k,v in pairs(ents.FindInSphere(ply:GetPos(), 500)) do
            emmit_bubbles(v)
        end

        ply.water_snd:PlayEx(1, 30)
        -- lowpass filter
        ply:SetDSP(31)

        local W = ScrW()
        local H = ScrH()

        surface.SetMaterial(blur)
        surface.SetDrawColor(255, 255, 255, 255)

        for i = 0.33, 2, 0.33 do
            blur:SetFloat("$blur", 2 * i)
            blur:Recompute()
            render.UpdateScreenEffectTexture()
            surface.DrawTexturedRect(0, 0, W, H)
        end
    end)

    local function draw_fog()
        local ply = LocalPlayer()
        if not ply:IsFlying() or ply ~= me then return end

        render.SetFogZ(5)
        render.FogMode(1)
        render.FogStart(0)
        render.FogEnd(256)
        render.FogMaxDensity(0.999)

        local c = render.GetLightColor(ply:EyePos())

        c.r = c.r * 0.6
        c.g = c.g * 1
        c.b = c.b * 2

        c = c * 255

        render.FogColor(c.r, c.g, c.b)

        return true
    end

    hook.Add("SetupSkyboxFog", "water", function()
        return draw_fog()
    end)

    hook.Add("SetupWorldFog", "water", function()
        return draw_fog()
    end)
end