Fishborg
If you control a face-up Level 3 or lower WATER monster: You can discard 1 card; Special Summon this card from your GY. If this card is used as Synchro Material, all other Synchro Materials must be WATER.
local s, id, o = GetID()
function s.initial_effect(c)
	--spsummon
	local e1 = Effect.CreateEffect(c)
	e1:SetDescription(aux.Stringid(id, 0))
	e1:SetCategory(CATEGORY_SPECIAL_SUMMON)
	e1:SetType(EFFECT_TYPE_IGNITION)
	e1:SetRange(LOCATION_GRAVE)
	e1:SetCondition(s.spcon)
	e1:SetCost(s.spcost)
	e1:SetTarget(s.sptg)
	e1:SetOperation(s.spop)
	c:RegisterEffect(e1)
	--synchro custom
	local e2 = Effect.CreateEffect(c)
	e2:SetType(EFFECT_TYPE_SINGLE)
	e2:SetCode(EFFECT_TUNER_MATERIAL_LIMIT)
	e2:SetProperty(EFFECT_FLAG_CANNOT_DISABLE + EFFECT_FLAG_UNCOPYABLE)
	e2:SetTarget(s.synlimit)
	c:RegisterEffect(e2)
end
function s.filter(c)
	return c:IsLevelBelow(3) and c:IsFaceup() and c:IsAttribute(ATTRIBUTE_WATER)
end
function s.spcon(e, tp, eg, ep, ev, re, r, rp)
	return Duel.IsExistingMatchingCard(s.filter, tp, LOCATION_MZONE, 0, 1, nil)
end
function s.spcost(e, tp, eg, ep, ev, re, r, rp, chk)
	if chk == 0 then
		return Duel.IsExistingMatchingCard(Card.IsDiscardable, tp, LOCATION_HAND, 0, 1, e:GetHandler())
	end
	Duel.DiscardHand(tp, Card.IsDiscardable, 1, 1, REASON_COST + REASON_DISCARD)
end
function s.sptg(e, tp, eg, ep, ev, re, r, rp, chk)
	local c = e:GetHandler()
	if chk == 0 then
		return Duel.GetLocationCount(tp, LOCATION_MZONE) > 0 and c:IsCanBeSpecialSummoned(e, 0, tp, false, false)
	end
	Duel.SetOperationInfo(0, CATEGORY_SPECIAL_SUMMON, c, 1, 0, 0)
end
function s.spop(e, tp, eg, ep, ev, re, r, rp)
	local c = e:GetHandler()
	if not c:IsRelateToEffect(e) then
		return
	end
	Duel.SpecialSummon(c, 0, tp, tp, false, false, POS_FACEUP)
end
function s.synlimit(e, c)
	return c:IsAttribute(ATTRIBUTE_WATER)
end


Fishborg
If you control a face-up Level 3 or lower WATER monster: You can discard 1 card; Special Summon this card from your GY. If this card is used as Synchro Material, all other Synchro Materials must be WATER.
-- Fishborg
local s, id, o = GetID()
function s.initial_effect(c)
	--spsummon
	local e1 = Effect.CreateEffect(c)
	e1:SetDescription(aux.Stringid(id, 0))
	e1:SetCategory(CATEGORY_SPECIAL_SUMMON)
	e1:SetType(EFFECT_TYPE_IGNITION)
	e1:SetRange(LOCATION_GRAVE)
	e1:SetCondition(s.spcon)
	e1:SetCost(s.spcost)
	e1:SetTarget(s.sptg)
	e1:SetOperation(s.spop)
	c:RegisterEffect(e1)
	--synchro custom
	local e2 = Effect.CreateEffect(c)
	e2:SetType(EFFECT_TYPE_SINGLE)
	e2:SetCode(EFFECT_TUNER_MATERIAL_LIMIT)
	e2:SetProperty(EFFECT_FLAG_CANNOT_DISABLE + EFFECT_FLAG_UNCOPYABLE)
	e2:SetTarget(s.synlimit)
	c:RegisterEffect(e2)
end
function s.filter(c)
	return c:IsLevelBelow(3) and c:IsFaceup() and c:IsAttribute(ATTRIBUTE_WATER)
end
function s.spcon(e, tp, eg, ep, ev, re, r, rp)
	return Duel.IsExistingMatchingCard(s.filter, tp, LOCATION_MZONE, 0, 1, nil)
end
function s.spcost(e, tp, eg, ep, ev, re, r, rp, chk)
	if chk == 0 then
		return Duel.IsExistingMatchingCard(Card.IsDiscardable, tp, LOCATION_HAND, 0, 1, e:GetHandler())
	end
	Duel.DiscardHand(tp, Card.IsDiscardable, 1, 1, REASON_COST + REASON_DISCARD)
end
function s.sptg(e, tp, eg, ep, ev, re, r, rp, chk)
	local c = e:GetHandler()
	if chk == 0 then
		return Duel.GetLocationCount(tp, LOCATION_MZONE) > 0 and c:IsCanBeSpecialSummoned(e, 0, tp, false, false)
	end
	Duel.SetOperationInfo(0, CATEGORY_SPECIAL_SUMMON, c, 1, 0, 0)
end
function s.spop(e, tp, eg, ep, ev, re, r, rp)
	local c = e:GetHandler()
	if not c:IsRelateToEffect(e) then
		return
	end
	Duel.SpecialSummon(c, 0, tp, tp, false, false, POS_FACEUP)
end
function s.synlimit(e, c)
	return c:IsAttribute(ATTRIBUTE_WATER)
end

